I played Persona 5 too, because I liked 4. I didn't like Persona 5 very much, although I completed it so it kept my attention anyway, although for stupid reasons in the end.
It starts off pretty well with all the Kamoshida stuff. I thought that was going to be the way of it as it went along, but none of the other villains were interesting to me. I dunno if the game gets worse as it goes along or if I just slowly realised I didn't like it. The writing is really bad, but not in an entertaining way. It's just extremely repetitive, clunky and a lot of the time barely even makes sense on a phrase to phrase level because the translation is so bad. The central concept is busted for a few reasons. Like you said Hundley, the antagonists are just a bunch of shitty people. They've got no depth to them except that they are bad, 'shitty adults'. None of the villains have an interesting arc because they all proceed like so - 1. bad adult is doing a crime. 2. the phantom thieves go through a dungeon while the adult taunts them. 3. the phantom thieves beat the bad adult and then the adult has a personality transplant and now they are a good person and then they disappear forever from the game. it's just flat, doesn't reallly go anywhere. The thief element doesn't have any relevance to the rest of the mythology or story, either. The game barely even remembers to include 'treasure' that you steal to 'change a persons heart' later on in the game, because it's been irrelevant from the start. It doesn't really fit, there's no coherence.
So they were fighting against all of that to keep the game engaging, but they didn't do it. The characters are just a mix of anime archetypes, and like I mentioned, the writing is just so bad it's hard to care about any of them. The thrust of the story is that these pure hearted teens want to change Japanese society for the better but it never goes into depth on what the problems are or why they exist, it just presents you with a series of one dimensional stock villains and then at the end you fight a god who talks utter nonsense.
I dunno why I liked Persona 4 so much, but I remember having a good time with it. I guess the characters in that one came off as more human than this one, which feels like a product targeted towards an audience who wants what they are used to and has a juvenile perspective on everything it takes to do with. The problems for me with it are big like the entire premise just being dogshit, medium like the romance stories being perfunctory and ugly, and small like the battle system not really being interesting enough to sustain the length of the game. I can't think of many things to say that I liked about it, except some of the music (there isn't enough music in the game though, a bunch of songs get played relentlessly).
I thought it was going to be some good dumb and good-natured fun, but it was mostly just boring.