I'm going to be the first one to admit that if someone was way, way better than me, to the point where I had absolutely no hope against them, yet I kept seeing them in matches... Yeah, I'd block them, if I had the option.
I don't play Overwatch but I play a lot of other FPS mp and that would kill the fun. I want to play against people my own skill level. Or in a team that has a mixture of my skill level, and above and below it on both teams (which is usually what CoD/BF do). Of course, CoD and BF don't give you that button so I have no choice but to suck it up hahah.