What really makes the show unwatchable, though, isn't the dull reused plot, or the predictable progression, or the edgy antihero, but rather that the show takes the overused "pervy character" trope far beyond the limits of what's enjoyable to watch. It's one thing to see iconic badass mentors like Roshi or Jiraiya get an occasional nosebleed to help balance out their otherwise near-flawless traits, but where My Hero Academia really fails here is that they instead attempted to attach that trope to "that one weak side character who's always muttering something about needing to get stronger to be able to keep up with the protagonist", resulting in an insufferable abomination with no redeeming qualities who you know is about to ruin your viewing experience anytime the damned little harbinger appears on screen.
Mineta, AKA The Grapist, is what would happen if you turned Scrappy Doo into a psychopath and allocated half his screentime to being useless and the other half to harassing or assaulting the other underage characters. Actually, nevermind, I guess that's still just Scrappy Doo.
