It's a bit of a pity then, since the primary strength of Watterson's work is his writing. His art is good, sure, but what made his name was the underlying substance, methinks.
He did it for fun (and for the charity auction). I think he should be able to do that without people complaining that they didn't get enough out of it.
(I mean, I think he quit, at least in part, because he'd said a lot of what he thought he had to say and started feeling like a turnip)