I'm still in "art school" - well, technically we don't really have that in Germany, I'm studying Communication Design btw (which is kinda Graphic Design+). In Germany, you usually are required to have a degree to land any jobs, even in the creative field, there are only a handful of exceptions to this and in general it is really difficult if you didn't graduate somewhere. (Also compared to the US, university is basically a free ride here due to no tutition fees.)
My school is very business-oriented so while there are classes that let you explore a bit on the artistic side, the general emphasis is on creating a solid yet creative concept and your design needs to work for that concept in first place. My studies definitely helped me in matters of typography, composition, and the overall cohesiveness of my creative output. It definitely makes it easier to distinguish good ideas from something that is just plain not working and to just start over again if something just doesn't work out as you like it. Some profs are really into kill your darlings.
Since my studies are very broad with typography, drawing/illustration, photography, editorial design, film, animation, interactive design etc. the thing I noticed the most is if you learn something in one medium, it usually transfers to the others in some way, and I consider this a huge pro for going to an actual art school. Even if you think you don't need it now, especially when you clearly know "I want to become X and do that for the rest of my life!" at some point it just ... helps you along and you don't need to hire someone to do it for you because you know how to do it yourself. Film is great for anything storytelling and also forces you to work in a group project and actually plan ahead in multiple ways.
That being said, I really appreciate that it increased my quality, my understanding of art and design as a whole and how everything connects in some way, however, I've never felt less creative than since I started art school.
In my last 4 years of school I probably had the highest creative output and basically drew on a daily basis, which kinda slowed down a bit during my 2 "gap years" but even in that time, I was drawing a lot more than I did during my studies. It is not because I don't have any time but somehow, all my energy is just ... drained. The amount of just sleeping or watching Netflix all day to somehow cope with this creative emptiness and lack of motivation whatsoever is where I struggled the most the last 2 years, it's even difficult to get through all your uni projects. This was basically also the reason why I dropped my comic and now have a hard time getting back to actually create for it again.
Right now I am in Seoul as an exchange student and only have like 1 class that is somewhat related to my studies (plus the student art club which is just a weekly drawing meeting with drawing enthusiasts), and while the first month literally flew by without me really noticing, I'm drawing and sketching more than in the last half year combined. It's like a knot finally dissolved.
I personally don't do well with a restricting schedule but also don't do well without, maybe that's one of my personal issues but uhhh... yeah.
Also another thing that I noticed: While profs say "oh well that'll look good in your portfolio" I never during all of these 2 years had the feeling I actually created something that I could ... show around and get a job from. Added to the pressure of "building my online presence," "having your general design projects eating your ass," and "guilt of not continuing my beloved comic" came "create a somewhat functional portfolio because all your uni projects don't feel right at all."
You definitely can create a solid portfolio without going to art school, I probably will land myself a retail job after uni and then just do that and work on my passion project of my comic again.
The thing is, it just really depends on what you're looking for, and especially for design, I find it more effective to actually go to uni for it, especially if you want to land a job in the field here.
Looking specifically at comics, I learned more about getting good at them on the internet than the sorry excuse that was my Comic class in 3rd semester but I still think the overall studies helped me get an understanding of what actually matters to me and what I couldn't care less about. I also had a bunch of real great professors who just encouraged me to do what I like so I didn't feel like I suck 100% at what I'm doing, to expand my horizon and just ... look at things from a different perspective. Sadly, the Illustration prof is none of these but in the end I think it doesn't really matter as long as you still have this type of prof.
I don't know if this is helpful in any way, also sorry for making it so long and disorganized... oh well. Good luck in the future for whatever you decide upon!