I spent a ton of hours on my first pokemon game, stopped after becoming champion in my second pokemon game, and then stopped before reaching the elite four in any pokemon game after that because they were essentially the same grindy game. I could beat every gym leader with my eyes closed. There was no challenge.
This game is so different it blew me away. Everything I disliked is gone. There's way less grind, you just tell your pokemon to attack and they level up. You don't run back to pokemon centers constantly because you can access your box and fly anywhere.
Most importantly of all, there's exploration with insane rewards scattered randomly around the world. It's not a linear path and you can have fun just running around seeing what's out there. I challenged a trainer and his pokemon were 20 levels above me and crushed me. I haven't lost to anyone since my first pokemon game. And it happened so many times. I was challenged, forced to explore different paths or sneak, and having to overcome all these obstacles was very fun.
The graphics suck and the performance is really bad. But, at the end of the day, it's the most fun I've ever had in a pokemon game since the first one I played over a decade ago.