I think a more comprehensive retcon would be required to make drow make sense. Their society seems to be self destructive on an unsustainable scale. But i suppose that isn't the the point here.
That's actually on brand for an unfortunately large amount of D&D worldbuilding. Few things make sense when you actually sit down to think about it in a real functioning sense. That's why we have stories about the D&D group that went on one adventure then stopped and became salt mining barons when they realised that salt mining is far safer and about as lucrative as adventuring. The entire "economy" of adventuring doesn't really make sense. Magical weapons are theoretically worth more gold than the average person can make in their entire lifetime, so the only people that can support this whole industry are adventurers, some of whom carry around enough gold to theoretically buy an entire city, except they can't because prices are all inflated for adventurer salaries. If a standard keelboat is worth 3000 gold, then how does any normal person ever actually afford one?
Just look at the Tiefling exponential. If Tiefs always breed true, even with other races, like the lore alleges they do, doesn't that mean there is an ever-expanding population of Tieflings that will eventually become the most populous, and then only, race? Except they won't because WoTC didn't think about that when they retconned Tief lore.
The question of whether or not these hidden Drow communities would have survived the spellplague is one that simply won't get answered, because not only are WoTC trying to pretend they didn't do that (because everybody hated it), but it simply wasn't something they took into consideration when writing the new lore.
