Anyhow, I think I'm going to avoid a wall of text and simplify every point I've made before to its most basic level. High Elves are different from Blood Elves in one major way, one that ties into every potential development path and even explains their low population.
They're Alliance. They're not only Alliance, but they're so Alliance that they're more loyal to it than Silvermoon. They cared more about what they wanted their people to be than what they were, and rejected their people in the end. A High Elf isn't particularly devoted to their culture or their people, it's their pride in other standards that sets them apart. And High Elves continue their grudge even after the Blood Elves gave up the practices they initially disagreed with, and the Blood Elves are perfectly willing to take them back.
When it comes down to it, the remaining Elves who still call themselves "High" Elves, rejecting the name change meant to honor the fallen, are pretty much more Alliance than Elf these days.