I've watched nearly all of the Marvel movies but I'm not sure I've watched any of them more than once. So if there was some mention of Thanos or the Infinity Stones in Iron Man 2 or whatever, then my remembrance of that is long gone (which doesn't seem unreasonable to me).
I think that this film could've benefited from a quite prologue that explains what the Infinity stones are and who Thanos is. It doesn't have to take long. Just a few minutes to give a quick overview and bring everyone up to speed.
I mean..this was all in the movie. There's a lot going on in the movie, but if you're paying attention, these things were explained. It seems like you came into the movie just expecting a "comic book movie" and didn't think you really needed to pay attention. I mean, you're saying it just felt like there was action after action scene, and that there was no real story, but most of the movie was about Thanos, and his quest to collect the stones and bring about his vision for the universe. These weren't just random battles happening in the movie-- each battle had a clear objective--collecting one of the stones.
As for the stones, what they could do is pretty much in most of their names.
*Power = power--this explains how effortlessly Thanos completely beats the shit out of Hulk in the beginning.
*Time stone..obvious.
*Soul Stone - They take you to some kind of "soul world" in the movie, and in order to get the stone you have to sacrifice something that you love--a life. That seemed pretty obvious that the Soul stone has something to do with life and death. I don't know the exact powers of the stone, but you get a good enough idea.
*The Reality Stone - Allows the user to create their own reality--the movie shows you this multiple times when Thanos alters the Guardians, and shows Stark what Titan USED to look like.
*The Mind stone--it's the thing that gave Vision intellgence and life--
*The Space Stone allows the user to be whereever they want to be--and Thanos uses the stone the second he gets it from Loki. It was all in the movie, and they SHOW you what the stones do.
lol Dr. Strange and Wong even go through a brief explanation to Stark.
Sounds like you just weren't paying attention. (i've only seen the movie once so far)
I like that this movie didn't baby the audience. There's no point in Marvel/Disney creating this movie "universe" and then not actually use it.
I think part of the issue here is that people want to put "comic book movies" in this 'lower tier' of movies, and they don't really show them the hespect they deserve because of it. These movies being based on comics doesn't mean that they can't have depth.