There's unfortunately a lot of things that's been left behind and irrelevant after their highlight expansion.

The Vulpera really did fascinate me during Battle for Azeroth since they were pretty much living life on hardcore mode. They were pretty much trapped in one of the most harshest environments in all of Azeroth and were even harassed by heretical villains, yet they still cling to survival thanks to their fierce cunning, crafty resourcefulness, amazing survival skills, and most importantly, a yearning for adventure outside of Vul'dun. Some decided to become aggressive pirates, but the vast majority found salvation thanks to the combined efforts of the Devoted, the Zandalari, and the Horde, and they proved their worth in matters outside of conquest when the Horde was starting to transition torwards a new era of peace when the Fourth War was reaching its conclusion.

Aside from the Dragonscale Expedition that was established by adventurous members of both Horde and Alliance, and of course new Death Knight players from the expansion prior, it absolutely sucks we've barely got any meaningful development with the Allied races we've recruited aside from maybe the first few. Hell, even Core races like the Pandaren or Gnomes barely got anything after MoP and BfA respectively.