If you don't play M+ for the sake of M+... why wouldn't you want to get your gear from a place you enjoy?
Wouldn't you rather do XYZ content if you think that's "better", "faster" or more rewarding to you and your game sessions?
I don't see how it would "cheapen" my experience when only people who want to enjoy M+ run M+.
Wouldn't it enhance it because I have people "pushing" keys with me?
Or people who run M+ because they feel like it's fun to do M+/more difficult dungeons?
Pretty sure I'd enjoy playing soccer with people who enjoy playing soccer more than with people who only do it because "you have to run and it helps them burn calories". No matter if they are bad or good in it as well.