This is the real reason Star Fleet is mostly human. Only very exceptional members of other species can stand working with humans. They even talk about this in Enterprise. Before T'Pol, the longest a Vulcan had managed to serve aboard a Star Fleet ship was two weeks. In Lower Decks, Captain Vendome built a crew of entirely Bolians. It's now my headcanon that this is because they just wanted a break from those damn humans. I believe there's also an all Vulcan ship in DS9, which was absolutely because they couldn't stand those humans.