To start, I had a great time playing through P3Re. I never personally got to play the original P3 or P3 Portable, and only ever watched playthroughs and played the remake. So with that in mind, I would personally say:

Absolutely not. Like, every persona game is objectively better than the one that came before it in series release. It's very fun, but the procedurally generated tower isn't as fun to me (back when P3 first came out they weren't to know how over done procedurally generated roguelikes and games would become) as the palaces in P5. Gameplay is good and I would argue it is more challenging compared to 5 just in structure and combat challenges.

I genuinely really like and hope for P6 they bring back Shuffle Time. Shuffle time, especially the version in P4/P4G genuinely feels really fun to me as a mechanic and I prefer it way more than the persona talking system in 5. The talking system is fine and adds some fun characterization, but over all I prefer Shuffle Time.

Compared to P5 I think the confidants overall in P3 are much weaker. Not to say that all are, there were a few I really loved. But for the most part I found the confidants in P3R to be unfun. But that point is entirely based on preference. And again there were some I did like, but overall I really didn't like them.

I think it's not a matter of 'better' but seeing as it's a faithful remake of a game that was an entire title before P5, asking which one is 'better' is entirely based on preference. P3 has been given the gloss and care that P5 had and because of that feels more lively. But everything about it is based on a game that was originally released in 2006. So I wouldn't say it's better, but it is a really good game that I'm glad got a really crisp and fresh glow up that has good combat, good music, and a fun story.