Your comment seems to present anecdotal evidence as facts about $framework's popularity. I think that's misleading.

I'm wondering if there's a scraper out there crawling Alexa TOP 1xxx pages for use of specific libraries, frameworks? Maybe that would present a more accurate picture about this.

Also it's often misleading since in any company with more than a few employees there seems to be more than one team of developers which often leads to different frameworks being used in different parts of the company. In $dayJob we use Angular in some legacy internal stuff, React in a rewritten consumer-facing project and preact or jQuery in a different consumer-facing project.

It's not that simple to determine marketshare of frameworks I think. We can just present different numbers and draw different conclusions from it, e.g. number of job postings mentioning specific frameworks, number of downloads in a registry, number of domains using it (assuming one app per domain), number of stars on github or number of people claiming to use it in the stackoverflow survey.

A lot of the web isn't publicly accessible. And most .com marketing sites are built on a much different tech stack than the actual product. Example: landing page is Wordpress, actual site is a SPA (be it React/Angular/Vue etc).

Builtwith.com does what you describe although not sure if it can detect react/angular/etc.

Not everything is public facing though, particularly in enterprise

"I've yet to see [React] used seriously at a BigCo" you realize Facebook a) sponsors its development and b) just rewrote their core product in it?

Might be anecdotal, but the new site is pretty rough.

c) I've never worked at Facebook so I've not seen their work and obviously I don't use Facebook.

I can name Google.