I was heavy into DBZ Dokkan Battle and in my first year of playing spent quite a lot of money on summons, just to get those new shiny characters that were obsolete the next month. Then I realized it's stupid, because I'm essentialy paying for a chance to obtain a low res JPG. So imagine my frustration when I would drop 60 euros, do my summons and get the worst cards in the game.
When I got over this mentality and went completely free to play, guess what? I was actually enjoying the game more, playing casually, doing some events, not stressing about this new Goku or Vegeta. In the end I still had an amazing deck of 600-700 characters, enough to clear any content.
And that's the thing with mobile Free 2 Play games. You don't need all the legendaries or whatever to enjoy it. You don't even need to play past the main campaign. Just have fun for 20-30-40 hours and drop it like you would do with a PC/console game.
So yeah, right now I'm having fun with Immortal. Should there be a serious paywall, I'm out and that's it. But I don't even care about leaderboards, PVP or best gear available, so it might not come to that.