Haven't heard the blues give any possible *solutions* to their customers, only acting defensive and trying to point out the fallacies in customers' arguments. So here is the ultimate breaker: if preventing flying is solely to "untrivialize" the leveling component (to wit: questing) then the solution is simple: just put the object of the quest inside a cabin, cave, underground, etc.
e.g. Quest NPC: "Hello adventurer, I took an arrow in the knee so I can't provide clothes for my family. Would you please fly halfway across this continent and kill bears and bring me back 10 bare asses so I can make clothes for my children? They are in that cave by that lake near that place way over there."
This prevents the tiresome argument of "...swooping in and killing quest NPC then flying away..." since what people aren't understanding is that the bitching is mostly due to the waste of time having to get to the area in the first place! We (at least, I) am/are not complaining about the lack of flying per se, only about the amount of wasted travel time, over and over and over, to get there and back. Once, is cool and fresh and exciting. More than that is a PITA and waste of time dealing with the S.O.S. every time (= boring).
So, I must conclude that the devs are forcing non-flying only in order to lengthen the time it takes to level, to force us to see certain lore to further their storyline, and to force us to see how beautifully they textured those new trees. Admirable perhaps, but they forget the golden rule of letting their customers play the game our way and not just their way.