A better question- Why does this thread exist? Why can't you just read the posts you're referring to instead creating a new thread to ask what they're about? All the answers you want are almost always in those very posts, had you bothered to look. I really don't know why you have to ask this.
The complaints waged against TDO or Meg Crofton or the company itself are generally in regards to their recent poor leadership of the WDW property and general unwillingness to spend money on keeping the parks and attractions looking and working as intended. These issues are brought up often because it wasn't always a problem. In fact, the problems don't even exist to such an extent in any of the other Disney parks around the world (not even Disneyland Paris). The complaints are very fair when you consider things like this happen at WDW on an ordinary basis-
http://www.youtube.com/watch?v=2Nv_xKKv2IQ
Not even the most diehard fans will try to excuse that (one hopes anyways). Seeing things like that compromises the experience for most people. Even small things combined in sufficient quantities (such as huge quantities of burnt out lights or wear and tear on the architecture) will interfere with the show quality. This lack of maintenance is a well known and widespread issue across all the WDW parks and property in general. We've even got respected insiders such as Lee, Raven, Martin, etc corroborating the stories of lack of caring within the insides of the company itself. Sometimes these issues go unfixed for days, weeks, months, or even years (if they're ever fixed at all). This is a failure at TDO's level, but also a failure on the part of the higher ups in the Disney company itself, going all the way up the chain of leadership to the very top.
Why do people complain about Disney? The answer should be obvious. If you don't know the answer, acquaint yourself with the concept of "standards" as well as "show-ready". And know that these standards of running the parks were not some unattainable pedestal set by naysayers or random minorities on the internet. These standards were set and practiced by the Disney company itself, it was once a point of pride for them in fact. Keyword "was", no longer is that way. That's very important.
Now another question- Why does it bother you so much that people don't share your unquestioning loyalty to the Disney corporation? Can you not enjoy yourself unless everyone worships the company as the pinnacle of perfection?