I don't see burnout or too many movies atm (heck just look at ever increasing box offices) but there will be a point they will sorta crash(marvel seems to be doing an okay job staving off the sameyness that the genre can have with the more oddball elements GotG) but I just can't see myself remaining interested in superhero movies a whole lot longer and I kinda get that feeling from friends and family. You see a marvel movie it will be good, have a mix of comedy and action, hints at the next movie/references to villians or heros upcoming.
CA2 was great but at the end I was just kinda like meh, I wish I had seen the raid 2, or stayed home and watch GoT. I'm psyched fot GotG but after that meh, days of future past, AS2, avengers 2, antman, all just do not appeal to me for some reason.
To keep me invested more needs to be happening, a major character needs to die, spidey needs to somehow show up for avengers idk just something and faster.
Its why i've enjoyed arrow as a tv show yeah theres filler episodes but there's always a new villian, and hero popping up(while not seeming like they are just throwing things at the wall) or some sort of drama happening.
TLDR version. Sometimes being good isn't enough.