Teacher deku isn't bad at all but it's wasn't built in dekus character and that's the problem. It's different from 430 bc we could tell deku wasn't fully satisfied and still wanted to be a hero, thats where the suit comes in to fulfill that dream. While 431 frames teacher deku as an end goal that deku always wanted while hero work is treated as more of a side gig which doesn't really work with the rest of the manga or his character.