Second, I use Debian and I have a fonts.conf that's hundreds of lines long, including dozens of lines of hinting settings because I prefer that some fonts use hintfull and others use hintslight. I don't have hinting settings for every font that exists, only fonts I installed, so when a site uses a web font, there is no dedicated hinting setting for it in my fonts.conf, and so it almost always looks worse than my default font.
I'd rather just view the page with the default fonts rather than wait 5-6 secondsfor the minimally different sans serif font that you've chosen for one paragraph that blocks the entire page render.
Hypotheticals aside, the fonts load sufficiently fast in a single round trip (two if HTTP2 push isn't supported), and do not block rendering.
I wish there was some font cache that could be shared between all sites, so once you downloaded a font it would be available for all. But I guess due to copyright it will never happen.