But for 16px and up, which is what websites of today use, serifs are perfectly fine even on 1× displays (though sure, they’ll look better still on higher-DPI displays, but so will sans-serifs).
I should clarify that it depends on the font. Sans-serifs tend to have fairly even stroke width, but serifs tend to have more variable stroke width, and if the thin is too thin, you get a terrible font. That’s a common shortcoming of serif fonts, and Garamond demonstrates that, being quite unsuitable for screen use below 20px, maybe even 24px. Others like Georgia don’t suffer that weakness.
Georgia is a terribly underrated font. I'm sure it's heavily hinted to look good at small sizes, but even at large sizes it has an elegance that is lacking in e.g. Times Roman.
[1] https://developer.mozilla.org/en-US/docs/Web/CSS/@media/reso...
If I see default browser serif, my immediate thought is "either this is an amateur or something is broken."