Just a real lack of substance, which was attempted to be substituted with just doubling down on the style, and while that style is really cool, I'm left coming away from every scene thinking "wait a minute, has anything even happened?"

You have fun interesting characters, that don't go anywhere and don't have anything meaningful to say, especially with Kanji and Naoto, are you fucking seriously telling me that the route we want to go with for this finding inner truth shit is "you need to accept these doubts as a part of you" but these 2 characters don't accept things, they just walk around it or just conform to societal standards.
Then they send it home with having weird, homophobic scenes, and having a horribly written character who's entire joke is that she's fat and gross.
Fantastic.
In general there's no real focus on the character's getting developed, and when they do it's really short-lived like with Teddie, and too much focus on having fun scenes with all your friends!!!
I can only assume the decision was made due to the VERY gloomy tone of 3, but the course correction was too harsh, especially considering this is a game about a murder mystery for crying out loud.

You have ideas that sound very clever on paper, but in execution are really, REALLY shit.
"I've got a great idea, we'll kill Nanako and throw the blame on the current suspect, and if you let that emotional vengeance get the best of you, you've let bias cloud your ability to find the truth and now you get the bad ending, and if you let him live, Nanako comes back because you've upheld Justice, and Nanako is the Justice social link!"
In execution: Nanako dies, pulls on the emotions, and now you have to look up a guide for how to do the next bit of dialogue or else you can't get the best ending because it's super specific, Oh, and Nanako's back now 10 minutes later, just incase you actually felt any weight to that death scene.

Actually solving the mystery is a little fun I suppose, but by the time the actual mystery picks up next thing you know you're getting sling-shotted into the "FIGHT GOD" part of the story, which I cannot stand, I'm sure you can send home the themes of the story without giving one last giant sledgehammer to the head of the meaning of everything, it's just corny as hell, I'll eat my words if this is any different in 5 but I'm expecting this trope to only be executed even remotely well in 3.
EDIT: Forgot to mention the extra parts after the "KILL GOD" stuff, pretty sure this is the super specific guide ending content, where you find the real mastermind that the game apparently needed to have, who gave people the power to enter the TVs, because this is something that needed to be explained, turns out it was a throwaway NPC at the start of the game and now you... fight OTHER God... What the fuck? Why was this necessary?

Also yadda yadda gameplay sucks ass, same dull Persona systems, but it's not freshened up like 5/P3R, RNG dungeons are never fun, etc.

I'm really curious for how this will end up when it inevitably gets remade, Atlus seems to have grown out of the shitty homophobic writing, the criticism for Kanji and Naoto has probably given them some time to think if there's anything to re-write, and in P3R there's more development added to a lot of the characters, as well as upgrading the gameplay from shit to bad, It could end up fixing a lot of the major problems this game has.

Maybe they'll even twist the atrociously bad drag show scene into something actually positive and salvageable, god, what the fuck were they thinking? Do happy and jolly vibes only come when you do the sacrificial punches down on minority groups?

I'm gonna keep it real, even with the nostalgia I have for this game and it being my first Persona game, this is easily the weakest in the franchise, even when compared to Persona 1 in my opinion.

I feel like a large amount of the strongest parts of the story don't come until pretty damn late into the game. Once Nanako is taken into the TV world is when the stakes finally actually feel high.
I can't help but not get as attached to this cast as I do with Persona 3 and 5. Yosuke is easily the weakest of the best buddy characters and the only character I have any emotional attachment to in the main cast is Rise, which to be fair, I am extremely attached to her.

Adachi is however, one of the most compelling villains in the franchise in my opinion, anyone could become him really.