- The previous films didn't require watching all of the rest of the MCU to hold up on their own. You absolutely have to watch all of the other MCU films to appreciate this one. This movie is basically a celebration of the entire MCU.
- The movie has an extreme editing challenge. The last one focused on Thanos, but this one focuses on the six original Avengers. It gives it a definite Lord of the Rings: Return of the King feel.
- Speaking of having a feel, this movie has the feelz. You know how all of the previous Avengers movies had the jokes? This took literally all of the jokes and replaces them with feelz.
- I would consider the previous Avengers film to be the actual climax, and this to be more of the falling action. Its emphasis is really on bringing everything full-circle and creating a definitive ending for this 22-movie saga; it wants to be more complete than it is big. But in all fairness, it's still the second biggest-feeling Avengers movie, so it's still pretty stinking big.
- It shows you some of the things with the characters that you always wanted to see, and thought, "When are they going to go for it?" Well, they finally did.
There you go. I hope that tells you everything you need to know in order to have the most satisfactory experience.