There is some interesting discussion in this thread.
The artist stuff is funny. The state of art is pretty good right now. I would say the top 30 artists are maybe better than the top 30 at any other time. I pick up a lot of books and they look pretty great to me. That said, the top 5 or 8 regularly working artists have been better at almost any time in the last 30 years. There hasn’t been that small handful of newish artists that everyone gets really excited about, who shows us new things, in a while. And that’s crucial. Ribic may be the closest newish one, but I think Marvel broke him with Secret Wars.
But the mean level of art is quite good, and the number of very good artists is long. There is an issue that the companies are publishing more books than even this amount of artists can bear, and that’s a big deal.
DC clearly seems to be winning the art game though. Their stuff, even some B titles, have art that is big and bold and expressive, whereas Marvel stuff is a bit on the stagnant side. Very talky, somewhat stuffy and confined, it rarely feels like a Marvel artist is given free rein to go nuts and have fun. It makes total sense that DiDio stresses this in that interview above.
As to what Marvel can do to improve their line. I think the answer is simple and staring them in the face: trim the line, space out the events enough that they start to feel special again, let the creators have some fun and truly build something on their books. It’s kind of like farming I guess—Marvel just wants to harvest, harvest, harvest, but you also have to give time to let things grow.