First of all- all companies tell their customers no, all the time.
If I phone up an all vegan food company demanding they make me bacon, they’ll tell me no.
If I demand lower premiums from my insurance company cuz I don’t like paying more money, they tell me no.
If I demand GRR Martin not kill off Ned, he’s going to tell me no.
Some of the best stories, the best parts of stories involve doing something that fans DO NOT want. Ned in GoT, Kamina in Gurren Lagann, Dumbledore, etc…
You’re also making the mistake of assuming that everyone wants the same thing. Frankly- we’ve already had flight, and when we do there’s people that hate it. Blizz also has explained why they stagger it- people skip content, it cheapens world pvp, it cheapens the experience in general, it changes entirely your viewpoint on the game.
We already have high elves- twice now, with belfs and velfs.
You speak of huge sources of revenue and correlation, but Cata saw the first major drop in subs after growing popularity from Vanilla to when subs peaked at the end of WotLK…
So let’s talk Cata. Did no flight kill Cata? No, Cata actually brought flight to virtually every part of the map (other than the draenei/belf starting zones), if your theory is correct Cata should have ‘brought in huge sources of revenue’, per your words- instead, it floundered and was poorly received by players.
Did no pvp vendors kill Cata? Again, no- it had pvp vendors, and other token vendors too…
Yet, WotLK peaked at 12M subs, and it did so at the end of the xpac, something that we don’t see any more. Cata ended with 9M.
So the xpac with the most flight, with pvp vendors- didn’t as you say ‘bring in huge revenue’- it actually killed a quarter of the playerbase.
From the looks of it, Blizz made the right choice.