These tripe ideas that have destroyed the legitimate, sensible, noble, goals of the left do come from Marxist Critical Theory and the Frankfurt School.
That is not what Will calls them, it is what *they* call themselves.
That said, in the USA, and only in the USA, you use Marxist as an insult. In the rest of the world it just means ideas based on the writing of the political philosopher Karl Marx. So it does not necessarily sound the way you are hearing it.
Now, I am not an expert but it seems to me that Marx was mostly concerned about class oppression, particularly economic oppression.
Then, a bunch of the subsequent Critical Theorists decided that that was too difficult and they would concentrate on absurd ideas instead.. ideas that try to defy and bend reality in favour of perception and feelings, that glorify virtue signalling, and, quite ironically, aspire to thought control.
Unfortunately these lunatics have claimed to be (or are) in the current of Marxism, and in so doing poisoned the well. So now if one is a rational thinking person and they care about economic inequality, these days, they have to find another definition for themselves...