And I have heard that it felt rushed to the theater.
It's hard to answer the other questions without giving you more context but I'll answer this one and this comment, that I've also seen myself on other forums, makes no sense.
This movie has been in in the works in conjunction with Infinity War. It's been in production for many years and clocks in at 3 hours. This movie is dripping with nuance and details. If you're a casual MCU fan, then some of the stuff might go over your head but what Endgame does is reward those who have been paying attention and care about these characters. If you don't, then it might look like another super hero movie to you, just bigger and grander. Which is fine as well.
My theory is that some people were expecting a non-stop battle scene for 3 hours and in reality, that wouldn't work. You would get over it very quickly. Not sure what others could've been expecting but so far I haven't seen a reasonable thought on it.