If I get your point, the controlling factor in entries for a Xword that appears in a newspaper is what that newspaper most often prints. This would explain why APU appears more than RODIN.
Newspapers are more likely to refer to pop culture than is, say, Smithsonian.
However, newspapers have always run Xwords, but the puzzles did not stress pop culture over traditional culture; they stressed tradition. I am noting a cultural change in newspaper Xwords.
Like you, I enjoy the diverse sources that comprise today's Xwords, which are less "academic," more fun, and perhaps more challenging for people like me.
Yet I do feel that we may be losing our most ennobling culture in favor of the more fleeting. I'd rather Tiny Tim refer to the Dickens character rather than to a ridiculous ukelele player because the former conjures a wonderful reading experience I had as a boy. That latter was an embarrassment.
But I'm an old teacher, and we pedants tend to mourn the loss of our youth.