I feel like BigWinnie's post sorta dips into why most of MHA's villains have kind of elicited a big shrug from me most of the time, or at least why redemption isn't fun to speculate.
In as much as I enjoy this particular villain arc, I kind of feel like Hori boned himself when bringing in the de facto "League" once Stain wrapped up. The original League when they were introduced were basically just thugs - with their only claim to fame being Nomu - but it almost feels like the post-Stain League was just kinda introduced as "here's the same brand of edgy kids; except these guys are more fucked up". We're introduced to characters like Toga and Dabi when they're already multiple cadavers into their villain life, yet that kind of runs antithetical to the Hero group who, with the exception of arguably Deku, have barely done anything worthy of being a hero (which is especially a point with Bakugo). While we're watching most of UA learning how to be a hero, that same dichotomy doesn't feel like it exists with the villains because they were already far into that business when we first met them.
MHA kind of has a problem of telling over showing, which is less of a problem for the heroes because we're still seeing them learn what it means to be a proper hero and pushing their own boundaries. That doesn't feel like it's really there for me with the villains because they've basically already had most of their defining moments off-screen. I think Dabi is justifiable, given that they're really leaning in on the inevitable twist that he's Shoto's brother, so it makes sense for him to have an enigmatic villainous past, but characters like Toga are already entering the series with a body count when I don't really know whether that adds anything to the story. Spinner is seemingly the only character supposedly "inspired" by Stain's morals to have possibly come into this business without a villain record on name. I feel like if they were really going for a "Villain Academia" idea here, we should've seen these guys start at the bottom. That's when you can start asking whether or not redemption is possible, imo. That's when you start questioning how far down some of these characters will sink, whether some of them will kill, whether some of them will have second thoughts about the ordeal, whether they think they're capable, because right now I don't really expect anything from these baddies outside of this arc just being a powerup/training arc to make the main bad guys relevant again. Even the protagonists have had multiple moments of them questioning whether they're worth it (it was notably the impetus of Tsuyu's heartfelt apology for making an assumption out of Deku, Kirishima, et al. going off to save Bakugo), whereas the villains generally don't have any of that stuff.
None of that is to say the bad guys are... bad I guess, because they are entertaining. It's just that I find it hard to really see them as anything but "bad guys", despite the series' effort to show them being troubled individuals. Most of these flashbacks they bring up to justify the characters kinda elicit a "well that's sad but okay" response from me, there's only so many times you can show a "society failed them!" story on screen without wanting something a little more substantive, given that all of it is text as opposed to subtext, and doesn't dig into the character nuances. There's a lot of action, but there's not enough "reaction".
All of this is to say much of this is why Gentle and La Brava are probably my favorite antagonists in the series thus far, because they actually develop away from the whole League "baggage" and we see a little more nuance to their relationship and what they want from each other, developing in the process. While society did "fail" them, it's taken in a more unique direction that focuses mainly on how they see each other. Extra side note; I really liked Rappa upon re-reading, especially how he basically had a tenuous allegiance to the yakuza and even helped Kirishima recover.