Have you ever spoken with the folks you're referencing? Here are some firsthand observations, corroborated many times over by others who encounter them:
1. They advance these issues insofar as they relate back to themselves and insofar as they themselves are included within whatever oppressed group is at issue.
2. They fixate upon "identity" and "lived experiences." In other words, they fixate upon themselves and imagine that they experience things others do not. I suppose selfism could be and is construed as an ideal in a dysfunctional society, but not in a relatively healthy one.
3. They propagate and celebrate fragility, weakness, intolerance, ignorance. You have these remarkable scenes playing out all the time of truly privileged Americans cursing the very systems and people that placed them in a position to be whining like this in the first place. Then you have folks repeating the chants and mantras we all know about multiculturalism, yet few of these folks could tell you the first thing about most any of the "multitude" of cultures they claim to celebrate. Like most Americans, they don't know anything about history or literature or anything of historical and cultural significance. How can you celebrate and appreciate cultures if you know nothing about them, starting with your own? You'll need to post a lot more evidence to convince me that these deep humanitarians have pushed civilization forward and are trying to push it even further ahead.
You can choose to believe that heterogeneity advances a society, but if solidarity is important, it works against that if we're discussing multiculturalism. The societies with the greatest solidarity are homogenous ones. You really have to be carefully taught not to believe that in order to set aside an obvious observation.