3 out of 4 most liked technologies are actually from Facebook, so the name certainly doesn't seem to prevent success here..
But there are many alternatives to Flow.
Angular is 4 years older than React, and generally speaking front-end frameworks have been probably the single most competed/overcrowded area...
Today we have Vue and others are forming in other languages, but still today angular takes a very different approach to the front end. But react’s breakthrough in the virtual dom management was totally new and really changed a lot of things in our industry.