I classify myself as a moderate pro-flier. I want flying in the game, I think flying is a good thing for the game and leads to a better played experience. But I do accept the argument that for new content it makes sense to withhold flying until the storyline progression is done.
I agree with you that I think it has been "shat upon" ie made the scapegoat for several problems for which it really isn't responsible, and this a huge annoyance. But I don't see why using it as a carrot, like in the pathfinder acheivements is a problem, provided the content they're using it as a carrot for is appropriate and fun.
The way I see it is that the decision should be based on the fundamentals of why flying is withheld in the first place - which is to make content that is experienced for the first time immersive (and therefore more fun). The main reason for flying is skip the travelling around that was fun the first time but has since become tedious.
From that perspective, withholding flying from Argus makes perfect sense. While it's current content keep flying out. But once we're done with it and the routine of dailies sets in - enable flying.
I am generally opposed to this way of thinking. Game design is a creative process that should not be constrained by silly restrictions like you're proposing. When they introduce new content, the decisions around whether to allow flying in those zones should be based on the new content, not on whether some players feel they've "earned" the right to fly. It's not about earning the right to fly, it's about introducing flight at the right time. Earning the right to fly is simply to make the process more interesting and gives them an opportunity to give us something to do (as opposed to simply activating it overnight).
As others have said, I think some people are reading far too much into Blizzard have said. They've communicated a design philosophy, to help us understand the why of what they do. If you insist on reading that as a promise of certain outcomes that you then feel entitled to, well, sorry to say that's on you.
What annoys me far more is that part of their philosophy I don't agree with. I don't agree that flying is the problem Blizzard think it is and that their reluctance to allow flying earlier stems from a false belief that the introduction of flying breaks their game. They need to understand that while the introduction of flying too early can break their game, the game tends to break itself with or without flying. And when it does break, flying is actually the salve that makes it playable.
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I find your use of the word "fair" very interesting. It also highlights the flaw in your mode of thinking.
This is not, nor should it be, about what is "fair". It is about when the time is right. The "compromise" in Blizzard's view is between when they think the time is right and our desire to have it now.
Really, this argument is very similar to a parent rewarding a child with sweets. A child may think that a parent who doesn't give it all the sweets it wants is being "unfair", since the child views the transaction as a reward for doing something. The parent on the other hand also has to consider the health of the child and recognises that too many sweets would be detrimental to the child's wellbeing.
Maybe there is an argument to be made that Blizzard is to blame for feeding this (false) perception of flying as a "reward" (as opposed to something that happens when the time is right). But then again I never really saw it that way - which is why I tend to view this attitude as a player problem.
I can respect arguments around when the right time to release flying should/shouldn't be. But this idea that I should have flying now because I want it/deserve it/have earned it, or it was promised to me, is just puerile.