GNOME and friends turned Linux-only a long time ago (if not from the start), but how problematic is that, really? Lots of Linux users and developers use classic desktops.
If end user software, such as Firefox or Libreoffice, became dependent on GNOME or other Linux-isms, that would be a real problem. I don't see that happening just yet (which may be to some great work put in by the ports maintainers). But I can't see missing out on GNOME as a very important omission for someone who has chosen to use an alternative operating system on their computer.