As an elf lover myself, I get what you're saying about elf popularity.
You're also right in that it doesn't seem like other races get anywhere near as much activity in their threads as elves do. I don't think night elf players get annoyed about nightborne in the same way as blood elf players do about void elves because nightborne haven't been given straight up copy/pastes of night elf assets, while void elves have been given the skin colors, and now also hair colors, of blood elves. There's also the fact that the nightborne model is noticeably different from the night elf model, while the blood elf and void elf models are identical. And now that void elves have both the skin and hair colors of blood elves, the main things left differentiating them visually are class availability, hairstyles and faction allegiance.
Personally, I also feel that some of the anger over void elves getting high elf options stems from some players being annoyed at the high elf requests over the years and seeing blizzard "cave" on it finally. There's a small segment of the playerbase who simply felt that alliance should never have gotten anything remotely in the neighborhood of high elves, not because of lore reasons (because we all know that high elves exist on the alliance today), but because they felt that once tbc gave blood elves to the horde, that high elves were "theirs" from that point on. Some probably also took pleasure from seeing high elf requests they never believed would be fulfilled, and now they are reeling from consecutive blows (the model, the eyes, the skin, and now the hair).
On the official forums, all they've really had left to fall back on now are barbs about void elves not having access to silvermoon or the paladin class, and the fact that entropic embrace turns them blue. I can only imagine how apoplectic with rage those players would be if blizzard allowed void elves access to the paladin class and/or allowed entropic embrace customization. Obviously silvermoon is always going to remain a horde capital under blood elf rule (unless blizz decides to "burn it" along with the exodar)
I think the best hope for any "focus" on blood elf requests is for dark ranger/san'layn options. Those themes are present as in-game assets already, and are also a long time request. Fel blood, light themes, and blood magic themes, all seem rather nebulous or niche in their popularity compared to the dark ranger/san'layn themes.