Sometimes I think I am the target audience for these movies.
In general, I like Sci-Fi movies. Star Wars is my favorite franchise, and the only one I followed "in depth", but I generally like Star Trek, LOTR, etc.
I never have read a comic book in my life. Didn't watch any MCU films till the Avengers came out, and I only Redbox'd it because I wanted to see the Cleveland scenes. I liked, so I went back and watched all the phase 1 moves, and enjoyed them. Now, I see them all in theatres.
It's great being a casual comic book fan. Since I haven't read any comic books, I never get disappointed about "botching" a charcter or story arc, because I never knew them. And if I need to do some quick research (i.e. Thanos or Infinity Stones), I can just go to wikipedia and get what I need in 5-10 minutes.
It's an already made universe that I can choose how far into it I want to go.