I've said this before, but I think #ContentWarnings are largely dead on #Mastodon.
I find it hard to recommend members of my instance use them when no one else does. I don't know if it's a post-Twitter thing, or if it's pushback against CWs being used to silence marginalized people, but I just don't see them used all that often.
I myself don't really want folks to use CWs for things like calling out racism/*phobia, but I do think we ought to use them for capital-P Politics news.