It was a decent game, but by no means a great game. Speaking on the mechanical side, it was very easy and failed to offer any challenge even on harder difficulties. I think the reason for this was because most of the bosses were very basic and didn't offer any kind of unique threat or challenge aside from "OMG-he's-charging-his-super-attack-better-guard-or-get-BTFO". Compare to P4, where most of the bosses were tailored to emphasize specific aspects of the game's combat mechanics and could very easily kill you if you disregarded said mechanics:
Shadow Yukiko: The importance of strengths/weaknesses and removing status alignments.
Shadow Kanji: The importance of removing enemy buffs and defending charge attacks.
Shadow Teddie: The importance of dealing with debuffs and status alignments. Also weaknesses again.
Shadow Mitsuo: Learning to pace yourself, deal burst damage, and covering status alignments and weaknesses again.
Shadow Nametame: defending against very high burst damage and surviving extended periods continuous high damage.
P5 didn't offer nearly as much variety aside from the first two bosses.