Just dumb, really dumb. Tonally it is all over the place, one second it's all bright shinny colours with Alan Silvestri style blockbuster score an upbeat tale of can-do genius inventor kids from the inner city, next second it's gritty gangsters and in your face black lives matter genius kids throwing all common sense out the window for hackneyed time travel save the day. And then it just stops. Not in an ambiguous way, just a kind of, hmm what else can we say about white cops shooting black teens for no reason, nothing more, okay let's just wrap it up then.

Dumb, preachy, doesn't follow it's own rules, bad acting, generally lame

Great music though. I can see what they were trying to do, make a genre film for a black audience. The problem is they took a white genre film script and peppered it with culture, instead of writing for an african american audience. So it comes across as looking like either white people trying to appeal to black audiences, or as black people trying to make a film that will promote their culture but still appeal to white people.

Net result is another sub-par Netflix film

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.

I think overall the movie was okay, but could have been a lot better with even the most minor of twerks. At this point since I've seen about 85,000 time travel movies I'm not looking for an explanation on how it works, but the movie doesn't do a good job at following it's own rules which is indicative of making it up as they go along. Any good story needs an outline that needs to be followed or it can fall apart at the seems.

I don't understand why the movie basically presented it as a "one or the other" deal with Calvin and Sebastian. Like no matter what, [spoiler] one of them has to die.[/spoiler] That part being the main focus plot of the movie is never explained and really doesn't make any sense, so it being the "glue" of the movie it's easy to see how and why things start crumbling a bit here. Then there's the ending, like alright I can buy an open ending if the rest of the story is pretty much resolved but this felt more like they were like "Shit, there's no way we're gonna be able to explain this, let's just call it a wrap."

So yeah, it had potential and wasn't unenjoyable to watch, but the more you actually think about it the more you're like "Wait a minute though..."