Yes, there's a genuine lack of risks these days! For every one story I've read that has a unique premise, there are one-hundred with the same foil, the same characters going to the same high school/college.
We're no longer in an era of pushing the bar; we're in an era trying to maintain the bar so we get noticed by Algorithm Senpai.
I'm not well-versed in the novels department (neither specifically on Tapas nor in general), but I'd like to add my 2 cents from the comic perspective because I'm absolutely seeing a similar issue there too.
A huge "problem" with dialogue in particular is that a lot of people don't write how people speak, but instead either focus too much on proper grammar (causing every character to have the same bland voice) or take inspiration from things such as oddly phrased scanlations, creating a really awkward atmosphere in their work. I imagine this kind of thing can creep its way into novel narration too, and the "fault" my be found in a lot of sources.
Now I say "problem" and "fault," but in the end this is me speaking from my own perspective because personally I love writing that feels "alive" and "organic." For all I know the type of writing I dislike brings joy to plenty of people out there, and that's totally fine to me so long as there still are writers who stubbornly do their own thing. 
Well, yeah. And thanks for bringing a new perspective on this discussion!
I liken most of these stories to comfort food: the potato chips of writing. And this problem certainly extends to novels, too. Characters are more so self-inserts or based solely on their appearance, sexuality, etc. It feels like dialogue in this instance is fulfilling a program rather than trying to tell a story. But hey, if it's cozy why get out of bed? lol.
Years ago when I worked for a magazine I had to interview an actress about a film she was in. She had the script with her on the table. I'll never forget this, as she spoke to me she put her hand on the script and softly ran her hand over it. I thought, that's how I want to write, I want to write so that someone would hold my work like it was one of their most precious possessions. That's where writing from the soul comes into play. You can use a program to correct your grammar but not to the point where it takes your soul away.
That’s my answer as well. I use ProWritingAid, free version, and treat its corrections as suggestions.
Also, I disagree with all prose feeling the same. I read quite a bit of books every day through club I am in, and I see everything, from ornate prose to deeply layered one to barely understandable chop-mush.
We should all be willing to try out what tools are available to us. Then, of course, pick what we want to use and reject everything else.
This is why I go through and individually choose which things get edited. Grammarly will offer certain suggestions regarding sentence structure and unless I see one I just really like I usually choose to ignore it. Punctuation issues and sentence fragments are primarily what I use it for anyway.
Having written mostly "spoken word" work (plays, audio drama etc.) most of my writing life before starting novels the past couple of years, I'm familiar with the subject of characters sounding alike. This doesn't mean that they should all have different accents or even regional dialects. The best way to learn the difference, really, is to listen to people. I've always been fascinated how different familial groups will speak with each other.
It’s hit and miss. Some stories I look at (and some of them are outside the club) blow me away. Some are hard to read. One I refuse to read because it drove me up the wall... I know that patchy reading is not the best habit, but I am exposed to so many stories each week it helps my writing.
I also have books and writers I simply follow because in some way they grip me. I maintain the Completed&Loved and Read This, Thank Me Later reading lists on Wattpad for outstanding books—in some ways.
Stylistically they are different.
Ants That Carried Us is impossible to mix with MADD Doctor or Wandering God or Renegade (well, Renegade fries my mind tbh) or Seacliff, but they all made it to my top books of the last couple of years.
I do think you have a point about people not knowing how to write how people really talk. It's like the tumblr post about writers not knowing how to write siblings with the "hi bro/ hi sis" stuff. Anyone with siblings knows that talk is weird.
I'm the same way. I prefer writing dialogue that feels organic and real instead of generic voices.
As a comic writer... none of this effects me (beyond spelling that is) XD in fact, comics have different workarounds to grammatical rules.
Not sure if this homogenous writing applies to contemporary traditionally-published YA books, since I haven't read any. But I think another aspect is that a lot of online works come from younger writers who haven't read a large breadth of books from different genres. They simply read other online works and so the "samey" beast feeds itself.
I can definitely attest to this homogenous writing problem. Honestly half the time I turn Grammarly off because I hate their suggestions, especially if I'm doing a dialogue-heavy scene and my characters aren't exactly "proper". I like @therosesword 's idea of writing "like myself", but when I do take inspiration I try to do so in terms of learning how to apply things to my writing. I've always loved the Douglass Adams quote "he flew through the air in much the same way that a brick doesn't", but all that did was make me mindful of just how much strength there is in thinking about how you can paint the picture in your reader's mind. If anything, we should be learning what tools we have at our disposal, not how other people use them.
