I'm a big proponent of replacing a lot of the old crappy stuff with newer good stuff. I think the fact that things like Backlot Tour, Universe of Energy, etc have made it this long without being replaced were a major negative to WDW. However I see them taking major strides to improve this (a bunch of things closing at DHS to build new stuff, Avatar and Rivers of Light at DAK, re-doing most all of DTD) I just hope this trend spreads to Epcot and MK.
That being said the declining quality of everything that seems to be rampant complaints on the boards is totally blown out of proportion. I can walk around the parks all day and see very little to no trash, the paint and landscaping look fantastic, the entertainment and fireworks are still top notch. People just like to complain because it's the cool thing to do.
Another thing that people are angry about is that they are being priced out but lets be honest Disney doesn't give a **** about that because their attendance is higher than ever. If you don't go but a rich family from China or Brazil does they are fine with that because statistics show they are going to spend way more money anyway. Even with the price hikes the parks are still crowded pretty much all the time, people can complain about how greedy Disney is but that's not going to change supply & demand.