Your all time favourite movie?
It's just that it actually lived up to the hype it generated. Usually these types of movies where they hype the crap out of it, end up being mediocre or complete let down.
Look at Batman V Superman, that could've been a great movie to watch. Or The Last Jedi. The hype for both was off the scale, but in the end both failed miserably for their own reasons.
Infinity War is not much when it comes to story, honestly there's isn't much to talk about the story in it at all, it's that anemic.
But that doesn't matter because we already had a lot of world building in the MCU, we know these characters, we've been following them for 10 years now and what over 12 movies or so, we know what drives them, how they think, we know the lore, we know the history.
All of it was a build up to the culmination of Infinity War. And in Infinity War we get action and action and action moment after moment. There isn't much of a dull moment to justify the run time of the movie, everything has its purpose. And it was amazing.
For those who have seen Infinity War, imagine if this was the second movie or the first movie in this cinematic universe. I guarantee you, you would've wreck this movie, just like another cinematic universe that gets wrecked by fans cough:BvS/DC:cough.
Simply because there would've been no build up to it. This is what DC failed and still fails to understand. They just shoved pretty much everything they had in one movie and expected the world to like it. It doesn't work like that. If they would've taken their time and done things in their own time and of course well, people would like it.
Because people have demonstrated if it's good they will like it. And in some cases even when it's bad they will like it. What they won't like if it's really bad, that's when they won't accept it.