I played this daily for literally 1500 days. I think this is the only gacha I've played that has good gameplay, and the only good mobile match-three game for that matter. You are allotted a set amount of time (depending on how you build your team) to make as many matches as you can. That simple change has it play drastically different from other match-three games and it allows for a high skill ceiling.
As for the actual gacha mechanic, it's generous with the in-game currency it gives out as I had only spent $5 throughout my time playing and that was only because there was an especially good deal at the time. The game is also generous with its gacha results; as in, you don't have to worry much about never having any good monsters to use as anything you pull will typically have a use.
The dungeon difficulties can get pretty ridiculous, but it just shows how much there is to the game. The ranked dungeon events also reflected that aspect when you compare yourself to top players.
I stopped playing because of burnout and I didn't like how the updates were scaling the strength of monsters which trivialized too many dungeons and eliminated a lot of team building strategies.
I had a fun time and made a good friend through it. It has enjoyable gameplay, depth, artwork.