This could have ended up as a few simplified settings, as presented to most users... as we have with light and dark modes. Colorblind themes (for multiple kinds of colorblindness, say), high-readability themes for people who need the large-print editions of books, that kind of thing. Doesn't have to mean making everyone pick exact point values for every type of H tag, or whatever. A few presets in a dropdown could be really helpful—again, just look how everyone goes nuts over something as simple as having a "dark mode" setting.