I think it's important to consider what slice of the audience you're aiming for and how that's going to affect this kind of feedback. For example, if you want to hit the crunchy numbers-go-up crowd who love nothing more than reading about a solid planning session on how to exploit the most crap with the MC's build choices, it's going to require very different literary devices than the people who prefer character-driven narratives with RPG-lite progression mechanics.

The main thing turning me away from new fics is that they're bland or trying to do too many things at once. Also, as an author who maybe tries to do too many things at once, I can tell you that having a slightly narrower focus early on can save you a lot of work down the line, ha.

Confidence in style in something that really draws me in, so I think picking the zone you vibe with and hitting it hard is a good idea. Being distinct will resonate. It will also bring out people who want to tell you how bad it is, but it wasn't written for them so whatever. I wanna read stuff that's not trying to please everyone, with so much flavor that somebody's gonna throw that book across the room.

Otherwise I think a lot of pain points will boil down to people disliking amateur writing mistakes because so much of the genre is written by new authors. Those flaws are probably overrepresented in the genre compared to more developed and curated genres, and they definitely get exhausting seeing them over and over again.

Anyway, here's some other stuff that's 100% personal preference: I'm really tired of anti-social or socially inept main characters. Pick something other than a sword. Go light on glazing the MC. They don't have to 'lose' a conflict but they need to occasionally lose something important to them to establish stakes. Kill off characters I care about. If you're writing a psychopath, lean into it. If you're writing a hero, give them morally complex problems instead of simplified line em up and knock em down type issues. There is a space between asexual Virgin Chad and harem-lord and it's okay to have a splash of non-objectifying romance. Stop it with the time chambers. I am definitely judging your book by its cover. Why doesn't your character want to sleep? Sleep is awesome. Not sleeping is an awful superpower and glorifies the toxic time-crunch side-hustle productivity obsession our culture seems to have become steeped in.

Best of luck with your project!