The game isn't well made. First it took two installs to get it to work as the first time it was just getting stuck on the lobby screen forever just showing the background image and nothing else.
It has long loading times especially at start up, it can take almost 4 minutes to get into the game.
It has a lot of bugs.
The first being the main story is broken so you can't access it, all that's available is events and resource grinding. This is a known bug and is going to be fixed apparently. It's the first time I ever played a mobile game where the main part of the game was completely broken even if it is temporary.
The game also crashed twice within 30mins. The first was an auto close of the game during combat. The second was whilst just doing a summon, the game suddenly went to about 1 frame every 10 seconds and then after around a minute completely crashed my whole phone and made it restart. This is obviously a bug that causes a memory leak which is a pretty severe bug.
I played this for a while when it first came out and it didn't seem well made even then. I was thinking it should have improved by now but it only seems to have gotten worse.