Interesting, I hadn't seen that reasoning before - that each vertical within the general-purpose RTS gameplay eventually split out into its own genre, if you will.

I suppose it makes sense, but makes me a bit sad as I feel reconciling the strategic value in one to complement another was the magic - resources, units, and towns only have value insofar as they enhance your strategic execution. I could never get into Civilization or Rollercoaster Tycoon where it felt (to me) like building just for the sake of building or following how someone else defines "good".