This is far from a perfect movie.
The opening parts leading up to Thanos dying (the first time, to be clear) felt pretty rushed. The pacing there just wasn't quite right; it moves through too many beats too quickly, at least for me.
The next part definitely works, though; the scenes of Scott Lang arriving in the future and working to establish what this post-Thanos world was like worked pretty well for me.
Then we get to the time heist, which I both enjoyed and disliked. There are a lot of fun scenes here - Cap in the elevator was fantastic, and getting to see Tony with his father was certainly heartwarming. Getting to see past events from a new perspective was great, and does a lot for worldbuilding. Problem is, it felt like there was way too much going on here. It sacrifices drive as a cohesive story for filling in all the smaller beats, and the whole thing felt messy and bloated. Some scenes could definitely have been cut from here, I'd say.
Then we get it - the final battle. Now, this part of the movie was fantastic. It's an emotional rollercoaster of ups and downs, and I loved almost every second of it. The whole battle has so many "blink and you'll miss it" moments, getting to see every hero we've come to know over the past eleven years working together to bring down Thanos and his armies. Cap wielding Mjolnir, seeing everyone come back through the portals, Pepper and Tony fighting side by side - I could go on and on about this ending.
One thing I wasn't quite happy with about the final battle was how little Nebula was involved. She has just as much of a connection to Thanos as any other hero in this movie - more of a connection, in many cases. Yet she just kind of gets sidelined when ti's time to finally defeat him. I get that she isn't the strongest hero on the screen - she can't throw him around Scarlet Witch and Captain Marvel can. Still, there should've been something for her to do. (There's actually a video by NandovMovies on the subject that I quite like, you guys should check it out.)
On a similar note, I wasn't happy with Hulk's arc in this movie, or rather, his lack thereof. All this lead-up to Banner and Hulk needing to work out what it meant for them to share a body, and they just resolve it. Off-screen. I'm not unhappy with the end result, though Banner's character felt a bit off for me. No, I'm annoyed that they just skipped straight to the end. I would've much rather seen Banner and Hulk still struggling to coexist and coming to a resolution over the course of the movie than just having everything be fine from moment one. As I said, this movie already has a lot going on, so it's not like I want whole scenes dedicated to just this. I do think that it's something that could color the interactions he already has though, sprinkling in moments where Hulk's angry, impulsive personality would momentarily overpower Banner's.
As a whole, this was a good movie, and a great way to end the past eleven years of the MCU. Don't get me wrong, I walked out of the movie amazed and quite happy with what we got. I like this movie. However, the experience was by no means flawless, and we get nothing out of pretending that it was.