I think MHA has one of the more interesting worlds I've read in recent memory. There was a lot to work with, but Horikoshi kept things mostly focused on battles.
I would've loved seeing more student and teacher backstory and interactions. More info on hero costume companies and weapons makers. The idea of advanced A.I. in robots was never explored. The Paranormal Liberation Front barely did anything of note. Star and Stripe visiting U.A. and developing a friendship with All Might and Deku in an mini arc before fighting Shiggy would've been nice. More could've been done with ReDestro making weapons for villains.
With other shonen series lately, I was done and ready to move on when they ended, but with MHA, I feel that way with the current arc but I wouldn't mind if the story continued in some way, shape, or form. Doesn't even have to star this cast. Give me a sequel to My Hero Vigilantes and I'd be a happy camper.