I'd still lean heavily on Sass for CSS development. Nestled rules is a particularly big feature in Sass, but not the only one which streamlines development and improves quality.

(With Internet Explorer's deprecation, iOS is now the browser which takes the most time for work-arounds and fixes. As you say, it is not ever-green like most modern browsers and its support for modern standards can break between releases. CSS nesting appears to be better supported since 17.2 back in 2023, but I've not tested it specifically, because well, Sass)

How much of your userbase is using Safari?