I had to go digging for it again and I've now bookmarked it, but this website/repo has some nice examples: https://modernfontstacks.com/
I do really wish that instead of moving in that direction, that customization was the norm, with sites specifying "serif" and "sans-serif" and users were assumed to be setting those settings to what they prefer. Similar to how dark mode is now respected on at least the plurality of "important" sites.
With built in fonts, if you want to support a wide range of machines, you have seven reliable fonts, one monospace and one cursive font to choose from. Georgia is a good looking serif font and I use it too much now, but the sans serif pairings aren’t great.
With CSS, you can make arial work as a heading font with a Georgia body for example, but that takes time and creates a testing burden. It only takes seconds to host a font that looks great out of the box and imposes a smaller testing burden. So for me the answer is a lack of talent that I’ve mitigated through transferring fonts on requests. I don’t think that’s a good thing, but my designs are no longer covered by a Geneva convention so that makes me feel better. :)