Humanoid birds are indeed more interesting than a race we already have with everything fun about that race taken away, turned into human bootlickers with a different eyecolor.
Ditto for the ethereals. And the ethereals were once humanoid. Dimensius ripped their planet apart with void power, reducing them to beings of naught but pure energy. The bandages keep them in a somewhat humanoid state. If they don't have those, they'll get a sort of "unbound" form, which looks like the specter model.
And the thing for both is that they are pretty much a blank slate with a few scribblings here and there. Those scribblings lay the foundation for them, which currently has a lot of potential. The ethereals can be so much more than "those space mummies". Same for the arakkoa. The truth is that you don't know much about them, and the things we do (the origins of their mummified form) is already pretty interesting. If they elaborate on them, they could be cool characters.
Same for the arakkoa, again. The arakkoa will be explored some more in Warlords of Draenor, where we will see many of them at the Spires of Arak. There is Old God foreshadowing, as well as Anzu and Terokkar laid out there for them. We also know that they had wings at that time, and that they weren't as.. weak and powerless looking as they are now. Warlords of Draenor could really turn the arakkoa into something more than what we know of them.
We can't do that with high elves. The only thing we can do is make their future interesting, starting now. What we know of high elves is essentially what we know of blood elves. They don't have a vastly different history from blood elves. This would be like making Mag'har orcs Alliance and advertising them as a new race. They don't have new looks, are only slightly different from an existing player race (more so than high elves are even), are only slightly different from the orcs we know, and are all-around just an empty addition.
The only difference is that high elves have a lore reason to join the alliance. Otherwise Mag'har orcs are a more viable option than high elves, even.
That's a good thing, because they won't be. At least, not as a new player race, unless everyone at Blizzard simultaneously loses their minds.
Good, because that it's one of the few acceptable and good ways to do it. If you want that, then, even if I don't like high elves, can support you. Why? Because they would be more options, and more options are just fine. I am against high elves as a new race.
There is:
They don't add anything. No unique aesthetic, no unique mounts, no unique culture, no rich, unique history. They literally are just color-swap blood elves with slightly different thoughts. They are too integrated in human society too, to have a proper culture. Maybe they can regain that, but right now, they're nothing but human bootlickers in a blue-eyed blood elf skin.
Do you?