Let's think objectively here.

Rating: 9/10 (15 September 2019)

First, let me say I've been an MCU fan since the beginning, so this review is from that standpoint.
To everyone bashing the use of time travel: So what? The writers deliver a twist in the first 5 minutes of the movie when Thanos reveals that he destroyed the stones and then loses is head. Soooo...where else did anyone think the movie could go other than time travel? To the writers' credit, they used time travel differently than most other time travel movies that I've seen. They're not trying to undo the snap or make it so it never happened. They're just trying to get the tools they need to fix it. So if you're at the movie because of time travel, I suggest you watch it again and really pay attention, particularly when Hulk explains what they're doing. Plus, the writers didn't only use time travel to achieve an objective, but also gave us some nice character development and resolution on the way.
I'm also seeing a lot of people complaining about the first act and that the whole movie is too slow. Well, maybe, but there's a reason for that. The MCU has been trying to show audiences that there are consequences to our heroes' actions/failures (Civil War, anyone?). The movie picks up 5 years after half of everything was dusted. The writers and directors took the time needed to show what the world was like now and show that the characters really haven't moved on from the Snap. They didn't want us to just see it. They wanted us to feel it. Personally, I did.
A lot of reviews are saying this movie doesn't make sense if you're not a MCU fan. Um...duh? No point addressing it beyond that. Go watch the rest of the movies.
I've also seen people say that Thanos is different and not as relatable in Endgame as he is in Infinity War. Again, this is on purpose, and after watching the commentary, it makes sense. Thanos in IW is more of a philosopher, 2014 Thanos that we see in Endgame is a butcher. He's not supposed to be likable.
A note about Fat Thor: at first, I didn't like that he didn't transform back into the fit, muscly Thor we expect. But the more I think about it, the more I appreciate it. There's plenty of explanations out there about it, so I won't explain it all here, but it can give you something to think about. It's actually really great character development.
Do I think the movie is perfect? No. Captain Marvel is a cool character, but I felt that she was used as a fix-all when the writers ran into a roadblock. Her finding Tony and bringing him back to earth was fine, but then she was conveniently absent until the end of the movie when they needed a good way to destroy Thanos' ship. And then after all of that, she still couldn't offer much of a challenge to Thanos himself. That was pretty weak and inconsistent writing. Also, I've nothing against strong female characters or the "feminist movement" (which I don't think really applies here but that's what everyone else who doesn't like it says), but the scene that highlights all the female characters felt a little forced.
Endgame strips down the 22-movie saga and focuses on the original team. We see our favorite characters come full circle and find the resolution they deserve. It is sometimes heartbreaking (Iron Man and Widow), sometimes satisfying (Cap), and sometimes in unexpected ways (Hulk and Fat Thor). It nearly perfectly wraps up the Infinity Saga while still leaving the door open for more stories. I haven't seen Spider-Man: Far From Home yet but I'm excited to see where the MCU and various Disney+ series go from here. 9/10