Flawed but quite enjoyable

Rating: 8/10 (20 May 2019)

Huge spoilers.
Except for Doctor Who, I hate time travel. That is mostly because too many stories use it to undo things, which is fraught with peril both to the characters and to the writing. Paradoxes are inevitable. So, one of my biggest complaints consistently about Marvel is that the writers don't stick to their own rules, or any rules. Magical things happen and there is no explanation or cost.
In this movie, the heroes spend a fair amount of screen time and angst explaining that you can't change the past. It is explained as if to say that ultimately it can't be done. This was by no means a small point in the story. So what does the story do? It changes things. Not the least of which is Captain America. And more to the point of the story, Thanos' history completely changes. (And how did he get that huge ship with thousands upon thousands of creatures through time?) Gamora's history also changes. And Nebula faces off with herself - that doesn't change time? In the present the three changed things and then none of them were there to do the things they did in the past, so the present should never happen. I hate time travel.
Also, there are at least three major love stories set up in Infinity War. The threads continue, at least to some extent, in this movie. And at least two of them crash and burn. While that is not necessarily a writing flaw, it doesn't make me happy. Of the three, I'm not even counting Jane. Why did her love story disappear?
So why did I really enjoy this movie? For one thing, the final conflict was awesome even if it was completely over the top. Another reason is that for 2 hours or more, there was a story with multiple threads. There was acting. There was humor. (I often think that Marvel humor is trite because they mix humor and tragedy with so little boundry, but in this movie, the humor was quicker and I don't know why, just better.) I loved big Hulk and fat Thor among other things.
Other nitpicks: My first thought when the team lined up to go back in time, lamenting there was only one chance each, was - why don't you go grab some more formulas from Hank first? I think the writers masked this problem a little anyway given they had to save some for returning the stones later. Turns out I was right, but they just hadn't thought of getting it from Hank, YET.
I didn't think the movie made it clear why Gamora didn't stick around for Quill. It was there, but you really have to think about it. My friend and I discussed it afterward and I didn't figure it out for a day. (She disappeared with Thanos when Stark snapped his fingers because she came through time to get there. And lest you say that explains my earlier complaint about her and Thanos changing their history, this still doesn't cover it because they still changed things before they poofed.
Others have complained about Captain Marvel's inconsistencies and disappearence. She tries to explain that there are other problems in the universe. But as one Avenger responds as she disappears, the mess left by Thanos is the biggest problem and it affects the whole universe. Clearly, her more timely help would have made things far less uncertain. (And that's why the writers had to banish her for much of the movie - drama. It's a reason, just not one that justifies the way it's written.)
So basically, my conclusion is - give me a fun, exciting story with good action and graphics (and some romance helps) and I might ignore the plot holes.