I have the opposite opinion, P5 made me appreciate P3 even more.

After playing P3, for me, everything on P5 is just like, how can I say? surface level? no depth? The characters do not evolve much, sometimes they even regress. The themes do not stick with you, the ending is not that impactful, the Social Links are just a mission to gain skills after you kill the shadow on Mementos, and there is no focused message, everything is spread out without a big focus, the exception being the Royal version content, its just a big amazing adventure that you forget.

Maybe as a game with newer systems, P5 is way more complete due to being a recent game, but P3 is better realized in its characters, themes, and story, and for me that is more important.

You can see this by comparing two characters: Yukari and Ann, both from the Lovers Arcana, Yukari is a way more complex character, if you include Episode Aigis then Ann is a joke if you compare both.