Earlier quoted context omitted.
I haven't but I'll give it a shot, thank you!
If you want to try their experimental GPU rendering (webrender) you can enable it via about:config -> gfx.webrender.all = true It works well on windows, I don't know how far the mac support is.
WebRender does work on macOS (and Android and maybe Linux), but Mozilla is prioritizing a Windows MVP first (because something like 90% of Firefox users are on Windows). Work on macOS, Linux, and Android will then resume.