You can't dismiss typography as irrelevant and trivial aesthetics. It's a whole field encompassing many things including legibility to humans. There's nothing more "functional" than principled crafting of legibility for each UI element. And no, a crude "Just use the same font in a single size for everything" approach is not the endgame for legibility.

Just because there have been some crappy industry trends doesn't mean the answer is to turn away and permanently regress to the confines of a terminal emulator.