I mean sure. I find mobile games, as a whole, just suck. I can't believe people spend time, let alone money, on them. Tiny screen, shitty controls, shallow gaming, poor battery life....I could go on.
With that being said, DI is probably one of the better ones Graphics are good for a mobile, gameplay is OK, still shallow compared to things you can play on console or PC.
So is this a game you can play for free, log on once in a while when you are bored? Absolutely. In fact, the better part of the game is probably the 1-60 levelling. Things really slow down and become a monotonous grind once you are into the Paragon levels.
But for FUCKS SAKE, DO NOT SPEND A DIME ON THIS GAME. Play it for free. Do not reward them even a penny for their predatory, pernicious behavior. If DI turns out to be a big hit, other companies are going to look into making more games like DI. This is going to affect the PC, console, and mobile gaming platforms adversely.