I disagree, unless you're talking leaderboard competitive M+ (which is an absolute tiny fraction of the playerbase) most people are pugging a lot. Since most people's interest in M+ is lost above a +15, it's not relevant to the discussion what people who are running 21 keys are doing, but since RIO exists people will still pug high keys, and I see it regular enough.
It's not 2008, pugging is a regular part of the game even for high level content.