Omfg yes, this 100%. I’ve been into IF for almost 10 years now, but in the last 2–3 I’ve been reading less and less IFs exactly for this reason. I can show some grace, because a lot of writers start out in fanfiction and tbh that’s not a bad thing in itself. Some great and even popular writers came from that space. I mean hell I do too lmao. I’ve been writing as a hobby since I was a kid, and when I was a teenager, I was just as deep into various cringe fanfic and the big YA trends of the time.
But there’s a point where you’ve got to grow up and branch out, read things that aren’t just fanfic or the same handful of YA tropes. And to clarify, there's nothing wrong with reading those too, as long as it's not everything you consume. I haven't read YA books since I was a teenager, but I do still read fanfics on occasion, when the mood strikes me every now and then. However, your writing should grow as your reading habits do. What frustrates me is how a lot of newer IFs feel stuck in this narrow creative loop, where the same tone, tropes, and character dynamics just get recycled endlessly. And there's nothing inherently wrong with tropes, they're popular and tropes for a reason, but in these IFs, it feels like they're executed in the same way, every single time, there's nothing new or creative.
Even when I was a teenager, the YA landscape was full of pretty cringe stuff like The Maze Runner, Divergent, Hush Hush and slop like that, but idk the vibe still felt different somehow, I can't rlly explain it. There was more of a sense of authors trying to tell a story or explore a world, even if it was messy. Now, with BookTok and this flood of copy-paste "romantasy" and “dark romance” content with cringe protagonists, nonexistent plots and shadow daddy romance interests, everything feels hyper-commercialized and self-referential. It’s like people are writing with algorithmic instincts and trying to hit trend checkboxes instead of actually developing tone, atmosphere, pacing or even thinking about their own story on a deeper level.
And yeah, this also brings me to my next point lol: I’ve def noticed how many of these authors are literally like 18 and fresh out of high school.

Which is fine ig because some of them do have great ideas and mature writing. For example The Exile by Pheo, like I'm pretty sure he was quite young when he started it, but that one actually had strong writing and mood, shame it seems like it's never gonna get finished. But as a general rule, as someone in my mid-20s, I just can’t connect with stories that read like brainrot Booktok fanfic dressed up as IF, especially when romance is front and center, it just feels weird fam

Like I'm not even that old lmfao but sometimes I feel like the "old man yells at cloud" meme.
This whole rant prob sounds like gatekeeping younger writers which isn't my intent, it’s more that the overall vibe of the medium has shifted. I miss when IFs felt weirder, more distinct, more experimental. Now so many of them sound like they were written by the same person with the same handful of internet references and the same character archetypes, and it just feels creatively stagnant, that's why I've been sticking with a few older IFs I fell in love with a few years ago and patiently supporting them and waiting for updates haha.
And also lmao yes to your last point, I have pretty severe ADHD myself and even my writing feels less scattered than so many of these demos bro
TLDR: Something something Booktok slop and its consequences have been a disaster for the human race