It's like coming in and watching the last 2 minutes of an hour long drama show and saying this episode sucks because it has no plot. It's utterly ridiculous!
There have been 31 marvel movies leading up to this point. All 31 has have some plot that leads to infinity war. Infinity War IS the end game movie. There is nothing left to explain, nothing left to discuss, it is all-out fight for control of the most powerful items in existence, the infinity stones. There have been 31 movies to explain in someway the power of these stones and/or the heroes that come together to fight Thanos in this movie. It's like a long game of chess where Thanos finally makes his move, and it's a huge one.
So I beg of any of you who reads this. Don't listen to anyone who says this movie has no plot, has no reason and is only fighting. They aren't worth listening to, Infinity Wars has roughly 60 hours of plot from 31 precious movies leading up to this monumental fight for life or death, and the movie is done to near perfection. The movie is glorious, the CGI is fantastic, the battles are awe-inspiring, and Thanos is made worth of your fear from the very beginning. He is truly the Mad Titan that captures your heart and crushes it right in front of your eyes.