I’m a bit late with this reply, but oh well… It seems to me that you equate your acquaintance’s position with actual linguistic descriptivism. But no, what he and you show is just different preferences and/or normative relationships towards language. Descriptivism (as in, the position that should be taken by a serious linguist) absolutely does not want to “flatten” language, it does not take a normative position, though it can/should criticise normative positions that are unavoidably based on unscientific notions. Those can include preference for “simple” language. Dictionaries don’t follow what’s going on at TikTok, so that’s just a non-issue.

Like, imagine a Christian talking with an atheist, and calling the atheist a Satanist. This is the same sort of mistake.

You are free to enjoy books with one sort of vocabulary, he’s free to enjoy books with an another sort of vocabulary. This is more of a matter of aesthetics, which we could also discuss, but I’d prefer to leave that aside or we’ll have to write even further walls of text.