It's sort of  like Louis CK's bit about wifi on the airplane not working "look how entitled you feel to something that didn't exist five minutes ago."

I think the reason we used to be excited for new movies all the time is because it's an issue of trust, there's still some people we trust to give us a good movie (Pixar, Marvel, etc) but because the process has become so open over the last twenty years, combined with the fact that audiences are savvier about the material they consume, they've become more discriminating.  Which I think is a good thing.  Having negativity be your default position ISN'T a good thing, but I think it's coming from a place where the movie fan has been burned so often.