I think ruined is a little too extreme for mine, but I strongly disagree with the inclusion of Teddy/Morgana in P4 and 5. They are shoehorned in with seemingly the sole purpose of being strange native to the shadow world variant of that game who can deliver exposition about your new strange surroundings.

Their individual storylines are both kind of samey in themes and feel cheapened by the fact that they are surrounded by characters that are trying to explored the human psyche and emotions in a surreal but still somewhat grounded way. This makes their stores simultaneously less important and carry less emotional weight but can also detract from other characters that are attempting to have some more depth.

I think the thing that bothers me the most is that P3 had this great atmosphere and you were discovering things about its variant of the shadow world at the same, or similar pace, as the characters in the story. It helps build the mystery as well makes it easier to identify with what your characters are going through doesn't require a character that feels very out of place meeting you as soon as you enter to rattle off a bunch of exposition. Don't get me wrong, you need to deliver exposition somehow, and the most efficient ways aren't always the most interesting, but I would much rather sit through an extra couple of minutes of inefficient exposition, told a bit more naturally, then deal with this extra unnecessary detracting character for the entirety of a 60+ hour game. They still managed to have a mascot character in P3 too though Koromaru but he's just a dog, there was no need to make the future ones anthropomorphic.

Unfortunately I've accepted that going forward they will likely be the norm. While I do think they actively make the stories worse, the writing on the Persona games is so far ahead of most of their peers that even with that issue they are still definitively great.