I love old shows, I love new shows. You just need to know where to look for the adult stuff. There’s plenty of it
I’ve watched nichijou, karas and they’re pretty good 
i’ve watched an episode or two of houseki no kuni and didn’t continue just when i’ve stopped watching all anime lmao, i guess i’ll check it out gain with the others. Thanks you
You'll get back into it. Part of getting older is realizing the things that you liked as a kid are still cool to like and the only reason you didn't like them in your early 20s anymore is because people looked down on you for it. I stopped watching anime around 20 as well. Now I'm 32 and It's non-stop Dragonball and Naruto all over again
Yeah, i looked a lot at adult show back then, noitamine being series for adults but i stopped looking somehow
Eh, i like children shows/cartoon a lot though and i’m not ashamed of liking them. It’s just the general feeling isn’t for me anymore i guess, or i just need looking for gems like i usually did years ago. I liked naruto then and still find so many problems with it then, not because it is childish but the female characters are handled badly
- Lupin iii (inspired cowboy bebop in the first place)
- Space dandy (inspired by cowboy and lupin iii)
These first two have a way more Saturday morning cartoon for adults feel. They’re both hilarious. Lupin is quite old but I recommend starting with the 1977 series. Not every episode is a gem, but it’s a good time. - Death parade (it’s beautiful and made me cry)
- Kakushigoto (cute father daughter relationship and very funny)
- Monster (literally the best anime I’ve ever seen. Also the most western and most mature. It literally takes place in Germany with all European characters except the lead, of course)
I’ve watched all of them except for kakushigoto i’ll check it out haha thanks i’m surprised people here have watched karas and monster because usually they’re very unknown 
Same tastes damnnn. Well what about black jack the 1990s ova series, heaven’s design team, sound euphonium and jitsu wa watashi wa
I’ve heard of black jack years ago but haven’t checked them out yet but i’ve watched trigun tho , from the posters sound euphonium and jitsu wa look too girly for me xD heaven’s design team looks right up my alley xD
I'm in my early 30s and I still watch anime, just not as many as I used to. Nowadays I follow about 2-3 shows per season, but it really depends on the lineup. The shows I tend to watch are those where I can switch off my brain, relax, and enjoy the ride.
Looking through the recommendations, I'm surprised that no one brought up Golden Kamuy! It's similar to Fullmetal Alchemist in nature, where you have comedic moments mixed in with the serious moments, and it has a compelling plot. Though, the author is a bit of a... strange person, so you may find some of the comedy a little too outrageous and/or unusual, but I'm having a blast with it.
jitsu wa is a school comedy about a boy who can't keep secrets and a girls who are all supernatural. his girl friend is a vampire and is class prez is an alien. it's hilarious and it doesn't even go the harem route. sound euphonium may have an all girl cast granted, but it's pretty deep in its themes and not actually very fluffy or cutesy. it's about quitting your passions and low self esteem.
I’m different because I actually picked up anime a few years ago and fell in love with a lot of it. I don’t watch it all the time cause of other priorities but still haven’t fell into boredom with it. I think spacing how much you do of something however can make that thing boring over time. Too much of a good thing can be bad and all that stuff...
I just go back and forth between different mediums. I watched anime as a kid, kinda was done with it, hopped back in in my late twenties because I found a title that interested me a lot and I was like "Yo, I should revisit anime!" For me it was S1 of One Punch Man, which really was so beautiful and hit a really personal chord with me in how it related to success and creativity and capitalism--just a really well done season (S2 sucks, unfortunately, because the anime industry is weird and gives shows to different studios)
So I think you just have to find the right anime for the right time in your life. I didn't like Deathnote when I first saw it. Then, I started watching it in 2020 with my Bro and was like "OK maybe Deathnote was exactly on the nose about a lot of things that are prescient right now" and now I like it.
I agree there's an overwhelming amount of trivial childish anime that is oversexualized, I think that has more to do with a small industry that uses the same creators over and over and is really hard to break into--some directors make childish things that are stereotyped and oversexualized and they just keep getting hired. Anime has a really big problem of only hiring people that they know, instead of taking a risk on new artists, and generally not paying people enough.
That and kids is the biggest market to sell animation to, so they get most of the attention. There are adult animes, there's just less of them. And as for anime that was really wild and progressive for it's time, those risk taking anime were made at a time it was cheaper to do that, especially in Japan. Now it costs so much money to produce animation in Japan, I don't think we'll see another cowboy Bebop anytime soon.
As for problematic stuff, the best way to combat that is if their advertisers and investors pulled from their problematic projects. That's how things have worked in other creative industries that were making problematic stuff, and why Western animation studios are so incredibly careful. It's not much of a big deal if people on the other side of the world are like "I'm done with anime" youknow, that's up to the big money back in the mainland. Not much we can do about it.
I see this problem as less "growing out of anime" than it is "growing up requires you to exercise more choice with your time." Since anime is just a medium and not a genre or specific structure, there really is a wide variety to choose from, not all of which are going to be presented to you straightforward and might require you to do some searching to find. If you base your idea of "anime" on what you just hear about from most people, you're going to get a limited selection of genres that likely appeal to whatever's trending at the time. When you're a kid and less familiar with archetypes and tropes, everything is new and exciting to you, but as you gain more knowledge you have to put more effort into finding new things (provided that's what you want and not just comfortable, predictable stories for escapism).
It's like saying you "grew out of films" because the only films you're being exposed to are whatever big blockbusters are being marketed (maybe less so nowadays considering the pandemic) and you feel like all films are just loud action movies. Or saying you "grew out of television" because you're only being exposed to safe family sitcoms or convoluted dramas.
Anyway, if we're doing recommendations, one recent anime I haven't seen mentioned yet would be Keep Your Hands Off Eizouken, which is about three high school girls who found a club for making their own anime. It completely avoids most of the problems of how mainstream anime handles young girls - none of the characters are sexualized or made overly cute and the main three girls are pretty rounded out as people and fairly unique in terms of not falling neatly into specific archetypes. The show as a whole also goes really deep into the process of creating anime and, considering the number of artists on this forum, I feel like a lot of people here would be able to connect strongly to the themes.
I actually really got into anime when I was at the end of college. Part of the fact was that in high school we had to stay up till forever to watch anime on Toonami and I usually had school and it was also hard to find sub/dubs online. Then when I got to college I didn't have time with sports and classes.
Now I actually have a bit of time here and there to watch series but it's very different than I would have watched in high school or college. I'm really picky now what I watch just because I don't have the time or energy to watch 10 different shows at once.
I like action shonen thanks to DBZ, but I don't really watch much anime beyond that but I know some.
Even so, I get your point, and I think it is due to the more anime we have today and the way it is produced for it to be competitive in the market.
More seasonal anime, made to last 12/13 episodes, while trying to be appealing to audiences following trends (super-heroes, isekais, "subverted" expectations at the start), and it ends with several animes that lack soul and just copy what other do but tweaking some elements that don't improve them at all.
And even in manga.
There have been improvements in the industry of course, (an anime of a popular shonen manga like MHA being paused from time to time to have less filler and adapt the manga better with good animation) but the problems are still there and growing (we are still accepting manga on weekly formats that take mangakas a whole week to make for a magazine that won't let them end until it's not profitable anymoret, just search for Oda's schedule and Kishimoto's thoughts on Naruto's length!).
There are more factors to it of course, and I think growing up and getting affected by the "adult life's realities" contributes to enjoy something less as well.
I'm still going strong at 26, but I think part of that is because of how slowly and casually I consume anime generally. Even at my peak speed in highschool and college, I still didn't binge through that many shows compared to some folks that I know, so I feel like I still semi-regularly stumble into gems or well-rated classics that I just had never gotten around to yet. For example, I thought that Assassination Classroom was fantastic, but just stumbled into it last summer, some 5 years after it had initially aired. Another example that I see mentioned in the OP, Haikyuu, is something that I just started this week. Thoroughly enjoying it, but I see it's been out for a number of years lol.
That said, I do obviously think it's okay to not be interested in a form of entertainment media anymore. There are tons of options out there and if you're not feeling anime anymore that's okay 
Part of why I get through it so slowly is because a lot of my time is also consume drawing, reading comics, playing games, etc. And that's all outside of work sooo, yeah i definitely feel the time crunch and need to be choosy with your time!