While using Inoreader in my browser this morning, I noticed a delay in refreshing the page. It turned out that the culprit was Google Fonts. Sure enough, as soon as I blocked that domain using uBlock Origin, Inoreader sped up dramatically.
This got me to thinking about other sites where I've noticed delays in opening pages. Since I use uBlock Origin, most advertising and tracking is already blocked, so perhaps Google Fonts (alongside Adobe Typekit and other web font libraries) are the cause? Inoreader is no less usable for having to fall back to system fonts and defaults, and I suspect the same may be true for other sites that I use regularly.
Of course, this site's current theme uses Google Fonts, but it's also fairly lightweight, so the delay isn't as severe. Theoretically, it would be possible to build a child theme that loads the fonts locally. And given that this is one of WordPress's own themes (Seedlet), I'm curious as to why they don't do this anyway, since it wouldn't add much to web hosting usage and an update could be issued if the fonts are updated. Too much extra effort?