I really don't get how people are even complaining about this. For Glory mode is only for online with randoms. Playing online with friends or playing offline locally, which is the way most will play if they are into competitive smash, still gives you complete access to all stages. So what's the problem exactly?
This whole thing comes across as bitching for the sake of bitching.
Sakurai is putting a lot of effort into making FD versions of most stages...and they aren't even all exactly the same. Sure they are flat but the different type of ledges on each can make a real difference. There seem to be a few differing lengths as well. For an online with randoms mode it seems more than fine...and also a pretty fun/cool idea that is poking fun at the whole Final Destination only meme.
Competitively people are going to mostly play local anyways, so the whole thing doesn't even matter...except now there are more FD choices.