The first mistake was a bit of foreshadowing that I can only describe as over-shadowing. Smart foreshadowing is the kind of thing you don't necessarily notice at first, but then when you look back on it you think "Oh yeah, the clues were there all along..."
The problem with the foreshadowing in Avengers: Infinity War is that it's just so ham-fisted. Or ham-gauntleted as the case may be.
What I'm referring to specifically here is the moment right after Scarlet Witch destroys the Mind Stone, killing Vision and apparently stopping Thanos and his diabolical quest to wipe out half the universe in its tracks.
The only problem? Thanos just uses the Infinity Gauntlet, now equipped with Dr. Strange's Time Stone, to reverse time and bring Vision back to life. More on this in a second.
The second big problem with the movie's ending comes moments later when Thor comes crashing down from the sky with his new axe (that's not a hammer, right, it's an axe?) and lodges it into Thanos's chest.
Thanos tells him he should have aimed for the head and then snaps his fingers. He's literally able to wipe out half the universe with the snap of his fingers and we start to watch as a whole bunch of our heroes (and just ordinary people, too) die. (The hidden scene actually reminded me of the opening moments of The Leftovers on HBO, which could be an interesting case study in how this massive genocide would impact society.)
In any case, we see a lot of our heroes die and some of them, like Spider-Man and the Guardians of the Galaxy (who all died except for Rocket and Nebula) have movies coming up after part two of Infinity War. So we know - for a fact, despite what any producers might say---that these characters are coming back.
And we have the foreshadowing of Thanos using the Time Stone to reverse what happened to Vision to clue us in to exactly how this might happen.
The problem here is that both these things happened. If only one or the other had happened, maybe it would have worked better. The reversal of time feels less like a clue as to how the good guys might turn things around and more like we're standing there with the Russo brothers shouting in our ears:
"Look we can go back in time and change things so nothing really matters!" Meanwhile, the fact that a large chunk of characters who we know can't die are included in the list of the dead only makes that more abundantly clear, undermining the emotional poignancy of the ending.
I would have rather Thanos just stopped Scarlet Witch or gotten to her before she screwed her courage to the sticky place. I would have preferred that the movie end when he tells Thor "You should have aimed for the head" and then snaps his finger, leaving us all to guess what happened.
I suspect the hidden scene in Captain Marvel will jump forward to her receiving Nick Fury's message and she will figure in prominently with Tony Stark, Captain America and the remaining survivors in their quest to undo what's been done. Which will almost certainly involve the Time Stone.
I could be wrong and this could all be misdirection but either way, however it comes about, these deaths all still feel pretty meaningless. As a small silver lining, at least it thins the herd for the next installment!
In any case, I very much enjoyed the film. I'm just still puzzling out how all this is supposed to work and whenever time travel is involved, the problems begin mounting up quickly (similar to how alternative dimensions can screw up certain DC Comics TV shows when not handled with enough care).