I'm sure somebody with a degree will have better words for this than I do, but it seems to me that culture goes in alternating modern/postmodern cycles.
Obviously those are terrible terms for the phenomenon but it's quite effective. "Modern" eras create works that exult in the formulas, "postmodern" eras deconstruct and question them.
This is a heroic myth stripped to the bare minimum. The fighting (here, at least) is minimized and often offscreen. The hero is ridiculous and not particulary puissant. The "drama" is dry and bare, and the real focus is on the characters and their interactions, the way they deal with this artificial situation.
"Modern" eras seem to produce a few really good things and a lot of credulous, imitative crap. "Postmodern" eras seem to produce a lot of different, really good, slightly boring work. It's hard to get excited about postmodern stuff, especially if you're kid.
We're definitely in a postmodern cycle with comics right now, pretty much have been since Jimmy Corrigan ten years ago. It's about to swing the other way but first someone has to come up with a heroic fantasy that people can actually believe in.
I would say that Sandman was a product of a "modern" cycle, like Image was. I think Watchmen and JLI would be the result of "postmodern" cycles.
Everything is always mired in stagnancy. The most experimental work is sometimes the most traditional -- notice the extremely classic and understated art of Watchmen, reaching back to before Kirby.