The monetization pressure is light if you don't go all out, but

Completely free-to-play is a bit tough, but with light spending, you can do quite a lot. As for the action, if you're using newer characters, it's genuinely good for a mobile action game. The story is quite long and complex for new players, and it's a pretty heavy Lost Apocalypse type of narrative, so it's definitely not for everyone. From my perspective as someone who's played since launch, I stopped reading the story midway through, and the events are getting a bit stale, so I'm getting bored. If you don't read the story, you might not be able to stick with it for long?