So I went and had a quick look and you are not wrong.
Let's say that vulvas appeared with mammals.
Mammals (well, the modern-ish kind of mammals) evolved about 250 millions of years ago
https://en.m.wikipedia.org/wiki/Evolution_of_mammals
Well, the problem then is that we're not only killing off all the bees but also other pollinators. Although, many plant species are also wind-pollinated and/or wind-dispersed. But good luck feeding all human life with this small selection of species only...