I've been playing since launch, and he game is a lot of fun. The characters are interesting and also the story and lore.
But the grind for materials to build a single character is very time consuming. Especially for 5 stars, who require more materials than 4 stars.
I have 9 characters semi-built at lv 60/70, mostly so I can deal with enemies of different weaknesses and it feels like there's not enough of an increase in the amount of drops when we reach a new Equilibrium Lv.
At least the puzzles are fun and make you think.