Looking at big companies is a bad metric if you're not a big company - or at least a rich one. Startups and in general smaller companies need to be very efficient with their developers, because they can't get many. Big companies have other issues, eg coordinating the work of thousands of developers, and choose their tooling accordingly.
Not that bad metric if you consider they had to start from something.
The argument on "rails dont scale" is that eventually you need to rewrite it. Which isn't actually true as there are many companies that continue to use it even though they've scaled, in product usage and employees.