I’m personally fond of Motif, even going so far as to hold XEphem as the epitome of timeless user interface design; I wish I had an entire OS following those blocky UI conventions. While normally using emwm, CDE would be productive and welcome on any of the BSDs and illumos distributions, IMHO.

Now if only OpenLook/XView could be made to lose its 32-bit cruft and become more portable. What a wonderful pair of desktop environments CDE and OpenLook would be to choose from—and perhaps add more functionality to—in 2025.