"I think we all generally endorse incremental improvements, instead of drastic overhauls."
Um, that is clearly not true, since otherwise, for example, the original poster would not have sent out his message.
For readers, I think many, if not most, would want a look and feel that works for them, aesthetically and functionally, regardless of how much a redesign was evolutionary or revolutionary. Many websites have gone through major redesigns successfully. (And of course some have been utter disasters, but many of those disasters came about because of poor design, not just because the design was a significant departure from the previous design.)
For WMF wikis with very small editor bases, the degree of change may be less important than the quality of the change. A meaningful change, however small or large, may enable that community to recruit new editors who were previously turned off by wiki syntax (or other) complexities.
As a WP editor myself, I would absolutely welcome a drastically different design, if it were a great design, that facilitated the editing and reading activities I want to engage in, and was pleasant to the eye. I welcome each change, regardless of size, that is an improvement.
One side benefit of a revolutionary design change is that it can make long-term users reassess their use of a website, sometimes discovering a "new" feature, which has actually been there all along, nevertheless creating more engaged users. Another, I imagine, is that often there is a spike in word-of-mouth surrounding a major redesign, which can also have positive recruitment effects. A third might be that a drastic redesign would re-level the playing field, so to speak. New editors might be less subject to poor conduct from some long-term editors who lord their arcane wiki knowledge over newbies.
Paul