How about the current arc?
It's relatively easy to pinpoint the flaws in the Rise of Villains saga, they're annoying, but they didn't seem huge enough to ruin the entire experience
The difference in the response to the current arc is what puzzled me the most
The current arc honestly is pretty much the peak of Horikoshi's writing mistakes in my opinion. And unlike before "jes wait 4 the next arc can't cut it anymore.
Just like the Vigilante Izuku arc they play up shit for shock value. Instead of the heroes being in a rigged mansion with the cliffhangers being "will they survive" with them getting out just fine off screen, its replaced with Bakugou's "death", will he get revived? Tune in next week (as if there's any question

).
Just like the other arcs Izuku uses his new quirks perfectly, making basically most of the cast superfluous. He only trained with 2 of them in the rest he literally learned while asleep. Basically cementing the 7 quirks as one of the biggest mistakes in the series when they're still trying to pedal how All Might was wrong and how multiple pillars are needed and shit.
Speaking of the cast except Endeavor (and initially Shoto) do basically fuck all. They literally can't do jackshit to Ashyraki despite the fact that his quirks are erased. Bakugou and everyone else are so worthless that they're honestly liabilities better off anywhere else. They placed Bakugou a mid range to close range fighter and Mirko a close range fighter against basically All Might and the readers are supposed to be surprised when they get themselves killed. Mirio can't do shit, the rest of the big 3 can't do shit, Bakugou the secondary protagonist, the rival mainly just gets his ass kicked so hard he starts crying

.
Ashyraki is boring as shit. He's always been a bad antagonist but he drags the story down. Ignoring that he could still kill everyone if he just....you know did it or that he could stop his quirk erasing by throwing a rock or something at super speed at Aizawa through the portal ( He's All Might lvl in strength so it's not like anyone would be able to react). You can't have that because he'd kill everyone, the power creep has gotten so ridiculous only Izuku and his dlc quirk pack can do anything. Instead we have him tanking everything thrown at him for 8 chapters for 1hp of damage. Oh and he can use a quirk- oh wait I mean a mutation bodily function that enables him to grow giant hands according to his will, which is different from a quirk somehow because something something quirk singularity. Even though that's not what singularity was stated to be but whatever

ha.
The crappy worldbuildng basically screws this series up once and for all. You learn basically nothing so this out of nowhere racism plot that Hori has had on the table for years comes out of nowhere. A chance to build up underutilized characters down the drain

. Hori knows it sucks too which is why he had to hand wave the whole thing by saying "oh mutant racism is gone in the cities that 99% of the series spends on but those countries areas man" shits stupid.
Izuku is just boring, I honestly don't want to explain the reasons why, dude straight up nears gary stu status and not the cool kinds. Also he's kinda an idiot, him getting looney Toons by Toga of all people and talking to her for some reason about dates basically screwed a bunch of people over.
The straight up dumbassary on both the villains and heroes in this arc

. Afo legit gets tricked by the Laser boy and Izuku's bad acting. The heroes planning gets even more retarded. "What's that close range fighters? Make them fight Ashyraki who can literally touch them and kill them instantly with his quirk and punch holes through them without it. "Oh you can't use your quirk in extreme heat? Help Shoto fight his brother whose flames are more powerful than Endeavor ". "Hey guys I know you know that teleportation guy that the villains want? Let's put him in a public hospital where civilians and doctors are at with their only protection being each other and weak people like animal boy. If they get in let's have the civilians hold hands and hope the mutant villains don't have the heart to kill them"

. Just an arc ago the cast (mainly Uraraka) basically dismissed the civilians concerns after they had their cities literally ran through, just a reminder

.
I could probably go on but I'd have to go through a lot of the previous arcs. Tldr the current arc suffers from Hori not knowing what to do with the series after All Might vs Afo and Vigilantes is much better than the main series

.