Maybe the failure of Civ V is not in the actual sales (although did it meet the infamous "projections"?), but in a failure to retain the goodwill of the fanbase and the presumptive supremacy of the franchise? The high marks in initial reviews were in part reputational, and even before the first game was played, Civ V was probably expected to be a contender for game of the year (presumptive supremacy).
If that presumptive supremacy has evaporated as a result of Civ V, that is a serious business loss. Who will pre-order Civ VI? Who will buy it before a playable demo is released? Civ VI enters the "fool me twice, shame on me" realm. Not the position any business covets for its product.
I don't see a problem with casual versions of Civ that are separate from the "hard core strategy" version of Civ. So I have no problem with Rev or Facebook Civ.
Except that the sun is shining today (at least where I am ... )
Actually, the Shafer departure must be due to the first lunar eclipse on the winter solstice since 1638!
dV