I think a lot of people (such as myself) go in expecting a fun/wacky action game. But it really is a puzzle game, where aiming for perfect scores and solving mind-bending problems are the core of the game, rather than mowing down hordes of enemies with weird anachronistic heroes. It's just not what I expected, and for that reason I couldn't enjoy it much.
Plus it's short. And that writing... eugh.
I mean, I was expecting somewhat of a puzzle game. It's just that for the base game, the solution to every puzzle is "rewind and kill that guy first." Also some classes are just so good that you rarely need to switch to a different class to overcome a challenge.
The challenge maps though, I quite enjoyed those. Because they were designed around forcing you to use your time travel powers in creative ways, in order to simultaneously complete multiple objectives, rather than just being a way to spray more bullets on the screen at a time until all the things are dead.
The medals where you had to get to a certain point within a certain amount of time though, fuck those things. I was able to complete them all, mostly by brute forcing them, but it just wasn't fun to do.