First of all there are whole genres which don't make sense with spoilers. Second, there are "normal" typical movies of different genres which can incorporate pl

First of all there are whole genres which don't make sense with spoilers. Second, there are "normal" typical movies of different genres which can incorporate plot twist to make a much heavier impact. For example kids fantasy movie Bridge to Terabithia, which even spawned some memes about child slave labor, because they went 100% in role. Sure, it's not worse now that I know the plot and it's not even the main point of it (as you correctly say), but initial impact was influenced a lot by watching it blind. Or the more recent firefighter movie Only the Brave which I randomly stumbled upon without knowing nothing about the basis of it, also made a huge impact. And again, it wasn't the point of the movie, but it made it much more impactful. This is all my personal opinion of course.