Surviving high elves comprise a mere 1% of the original high elven population, with the blood elves accounting for the remaining 9% of it.[2][7] Since Kael'thas took 15% of the blood elves to Outland[7] (i.e. 1.35% of the original high elf population), and since Kael'thas' army numbered at least 2,000 ("thousands of them") according to the Excerpts from the Journal of Archmage Vargoth, it follows that the total high elf population is currently at least 1,481 (and at least ~148,000 prior to the Third War).
In relation to the playable races, Blizzard has stated that the high elves have a considerably smaller population than even the Gnomeregan Exiles.[36] High elves are a rare sight even in Alliance lands,[37] and are considered a fallen, all but extinct race.[38]
With the destruction of both Theramore and Quel'Lithien (along with the de-canonization of the RPG sourcebooks), the bulk of the remaining high elf population appears to be bound to the Kirin Tor's Silver Covenant, Outland's Allerian Stronghold, and Hinterlands' Quel'Danil Lodge.
https://wow.gamepedia.com/High_elf#Population
The high elves cant even begin to compare to blood elves in number, something Blizzard emphasized before all their casualties in WoW.
The void elves break the population argument for subraces, they were described as an elite squad, not a sizeable populaltion, they are likely one percent of the blood elves if that.
Population however is not the reason you aren't getting high elves.