I've read several times in this thread(& in other threads & forums), how some people dont enjoy MHA as much as they did before and a few days ago someone mentioned how important an antagonist is for conflict in story(was different topic), and I think that is one problem of My Hero Academia at this point-
The lack of tension.
One of the oldest rules in stories is, that the hero must struggle. But ironically, at this point, it's the villains who are really struggling in My Hero Academia. The League of Villains still licking their wounds, they've lost one member and another one was heavily wounded, and with Twice we have a character, who is suffering extremely for several traguc reason.(not painting the members of the LoV as tragic persons, bc Dabi is a mass murderer & Shigaraki a psychopath, but Twice got a lot of screentime in this arc)-
And the heroes side currently? We have Deku's class, the other class, the Top 3 students of UA, we have the rival school and on top of this dozens pro-heroes.
Even if the count the Yakuza to the villain side, even they are in a weak state & trying to get to the top again.
I would say, that by sending the big bad All-For-One to prison Horikoshi actually hurt his manga after all. There is no real threats left, besides Shigaraki's group and they're not in the best state at the moment. Horikoshi should've established other villains or even villain organisations to keep tension high. Of course, I know, that the League of Villains will become a greater threat later on and we just see how they grow to power, but in One Piece we have the rise of Blackbeard AND the threat of the other Yonkou(edit: and the Marines, complettely forgot about them) in the background(and yeah, I know,it's not a perfect example).
And I know, it makes sense, why this is, because we were in a golden era of heroes thanks to All Might, and having other villains for the sake of having them, is not the best solution, but at the same time, having only a few villains, who are actually struggling vs A DAMN LOT OF HEROES isnt that interesting right now.
It's just one reason, why I think, people arent that happy with MHA at this point(not THE reason), and I'm aware that we are in an arc, which could change things a lot(if Horikoshi dares to change the Status Quo), but for me it's an important aspect that the heroes must struggle inevery stories, and especially in Shonen this can be done by having strong & threatening villains.