its an e-news cliche, but PLA is a decent game but a bad pokemon game. from a pokemon game, i want long-term appeal i could theoretically play infinitely. shiny hunting, battling in facilities and online, etc.
PLA is inherently finite. no matter how much of it takes your fancy - i know a guy who perfected every dex entry and went for a shiny living dex - whenever you finish that, its done. the game has no more appeal. the guy i know has dropped the game - he cant further perfect the dex, or catch any new shinies. its a fun game to play through, but it doesnt have the same appeal as mainline pokemon