The culture in multiculturalism seems to boil down to restaurant and pop (i.e industrial) culture choices. If it is anything beyond that, it is utilitarianism: the rule of numbers, economics. Capitalism in other words. Any attempt to assimilate the cultural change happening today to that of the past, or to validate it by what happened in the past, is fraud and diversion.
Ἄρρητον means "what is not to be spoken". I'd say the maxim is purposely ambiguous rather than baffling. It could mean "shameful", "horrible", or "sacred".
In high school I thought Hamlet was a comedy. All the characters seemed deluded to the point of foolishness. The ending is a perfect comedy of errors. My feeling was good riddance!
That was Milton Friedman's view.