If we look at the complaints we can see some similarities with complaints of prior editions:
1) Names - This is sort of like the problem we had with Tasha's Hideous laughter, Bigby's crushing fist or Mordenkeinen's sword. They were Greyhawk names, and you might have wanted something a little more generic for your setting, or use your own names. Most people didn't bother, because a) they didn't stick during gameplay or b) you have the conceit that they were archmages buried somewhere in the history of your campaign.
The paragon paths are a little different, in that they are both active schools, and feats and class abilities attached to that school. I myself don't really see a place for Golden Wyvern or Emerald Frost in my campaign setting (though I do have culture that fits Iron Sigil). Regardless, I'm going to want to use the feats and magical attacks associated with that school, so I'd rather not have their name on them because of reason (a) mentioned above. So if I was (for example) to call an order of War Wizard Evokers "The Academy", I would probably find them mentioned by players as the "Golden Wyvern Academy" pretty quickly if I based it on that order or a few of their abilities. Not quite the same elite menace I was trying to convey.
2) Not anime enough - The complaint that a spell's school didn't really fit its effect in 1-3e is similar to the complaint that "Golden Wyvern" doesn't really explain its theme or philosophy of magic. I would certainly expect a school called "Iron Sigil" to use an iron orb as a focus and create magic based on sigils. It certainly is much more cinematic. Like fighting styles, if it was based on an animal, you would expect it to have abilities that evoke that animal. The Black Crow Witches for example would have a shrieking attack, and dissolve into a pile of black feathers when they teleport.
I was kind of hoping myself that since we were getting rid of the Vancian magic system that we would be easier to design our own types and philosophies of magic by having standard ways of attacking, effects, and so forth so that you could leave the flavor text to define a lot of how the magic functions. This seems to go against that principle.