A point I've seen made regarding the reception to MB is that while it appears negative, it's only the same few thousand people posting hte same negative opinions on Youtube, Twitter, the forums, etc. so the negative reception isn't indicative of the thoughts of the casual park goer, who is likely thrilled to have a new ride experience, or even worse, impartial to having a new ride. When a video receives numerous dislikes, but only a few likes, it's hard to believe that that's just the die hards skewing the results. It almost has to be a sign that overall, the public is either unaware, doesn't care, or isn't happy about the change.
While I'm simplifying a complex subject, the thing that sticks out the most is that it lowers the quality of opinion of the fans, or those with an attachment to the ride. Shouldn't Disney care what their die hard fans think and want? We may have a reputation of being resistant to change, but I think we're mostly resistant to bad or unwarranted change. Most on here would argue for a Tomorrowland reimagining. An overhaul of Toontown. An extensive Matterhorn refurb.
There is also the argument that we'll go anyways. We love it to much, so even if they alter a few things we will still keep coming in droves. But especially in DCA's case, that might not happen. I haven't stepped foot in DCA in two years, but have gone to DL Park multiple times. The AP holders could start skipping MB, as opposed to making it a ride to go on every time like ToT.