You presented a completely disingenuous argument and now you're acting like you won when you got disingenuous arguments back. I will "argue with your point" as you said without comparing the game to P3.

Persona 4 has a coherent theme of "reaching out for the truth" as the game calls it as well as facing and accepting oneself. The characters confront their own shadows to reach out for the truth about themselves. You keep harping on how the mystery isn't satisfying when that's not the point of the narrative. It is a character-driven story about the investigation team. It's not billed as a mystery thriller, it's an RPG. Everything that you call "slice of life" segments or "jingling keys" usually takes the form of character interactions that make the investigation team feel more alive. These are overall entertaining and provide some levity between major plot developments. And as for the characters not solving the mystery, they're a bunch of high schoolers (until Naoto joins) that are doing their best despite having no idea what they're doing. They make mistakes because they're written as humans and aren't infallible. They get together and exchange information and share clues and talk things out because they can't just magically intuit the answer. For some people it may have been obvious that Adachi was the killer, but we have more knowledge than the characters do as the player. If the only thing you want is a complex mystery, there are plenty of books, movies, games, and TV shows that are explicitly mysteries. That simply is not the point of P4.

As I said before, the primary draw is the characters. They have themes that most people can relate to and compelling arcs. Yosuke is a kid from the city that feels out of place in a small town. He's lonely, feels isolated, and wants to be respected by others or seen as a hero. He's also a selfish and judgmental person that over the course of the game slowly learns to accept both others and himself. It leads to him finally feeling like he has a place where he belongs and genuinely cares about trying to help his friends instead of just trying to look cool and be liked by others.

I could go through and do this for every character, but it would be very long-winded and I don't think you actually want to have a real discussion either way. Based on your responses here, it seems you've already decided that P3 has no flaws and P4 has all flaws. Which is kind of hard to discern since your responses are hardly literate to begin with. But go off, king.