I'm really not sure if this is a good movie or not. For starters, I enjoyed it. It was an interesting, engaging story that's paced well, and the #BLM stuff is handled mostly pretty well.
There's a bit of pretty cringey pseudo-science in an attempt to explain the time-travel, but it's easy enough to ignore.

There are two big flaws though.
The first flaw for me was in the time-travel inconsistencies. Particularly how they set up a number of limitations and narrative obstacles, just to "deus ex machina" them away as soon as they become an actual issue. Or even worse, they just ignore that they previously established some limitation and do whatever.
[spoiler] For example, Sebastian mentions before the first jump back in time to try and save Calvin, that they can only make a jump once a day. It's never explained why, but later in the movie CJ makes multiple jumps in the same day, without repercussions. Also, when they're prepping for their second attempt, Sebastian introduces an obstacle of having to avoid running into their first-attempt selves. Instead of dealing with that, they immediately just solve the problem with previously-unmentioned gold motherboards from Eduardo. [/spoiler]
If you're a time-travel pedant, you're probably not going to enjoy this. There's too much left unexplained, or with explanation that doesn't make sense.

The second big flaw is that this movie doesn't really utilise the time-travel to any meaningful end. A good sci-fi story is about a lot more than just the events of that story. They usually have something to say about humanity, or society, or the like. However this movie seems to have chosen to say what it wants to say with the movie's setting and the time-travel adds very little to it. I walked away wondering what I was suppose to take from it all. And sure, not every movie needs a moral, but when your movie is about [spoiler] police brutality and gun violence [/spoiler] you really should have something to say.

Also, while I can accept an ambiguous ending, this one was pretty unfulfilling and lacked any sort of closure.