> You could also have a Safari content blocker with an optional WebExtension for additional functionality with no usage of DeclarativeNetRequest.

That’s exactly what AdGuard and some other content blockers do. The result is that content blocking works everywhere, but it’s most effective in Safari. As a user, I prefer that over the approach of uBlock Origin Lite, which is a pure WebExtension and doesn’t do anything outside of Safari. Too bad, because I prefer using uBlock Origin on other platforms.