Your post is a bit misleading. Rails can scale but to get there is different than with other stacks. Some would say, it's much more challenging or complicated, some would call it just a PITA and if you really, really want to scale, like e.g. a porn site, Rails is the worst choice you could ever take. Or you would just completely rewrite it but what is then the motivation to take a framework? Maybe frameworks are wrong...?
However, I think dev productivity is more important since scaling is a requirement which is very often not needed and introducing it too early is just premature optimization.
Still, I dislike if people spread false information. Rails can scale to a certain (limited) degree but it never was easy, just the deployment then without Docker was a big mess (I didn't know one Rails guys who could deploy anything without Heroku).
So let's just forget about Basecamp, Github, AirBnb, Hulu, Kickstarter, MyFitnessPal, Twitch and all the other Rails sites and continue to pretend Rails can't scale and won't work for the modern web.
Basecamp is always on the latest or beta version of rails, Rails 6 at the moment. GitHub has recently updated to version 5 and are merging a large mount of their scaling gems for version 6.
There are some podcasts and keynotes where DHH talks about their stacks.
Hulu was, and possibly still is, a Rails site. Streaming video is no problem for a Rails based application because the application server just prepares a URL for nginx to stream.
Your post is a bit misleading. Rails can scale but to get there is different than with other stacks. Some would say, it's much more challenging or complicated, some would call it just a PITA and if you really, really want to scale, like e.g. a porn site, Rails is the worst choice you could ever take. Or you would just completely rewrite it but what is then the motivation to take a framework? Maybe frameworks are wrong...?
However, I think dev productivity is more important since scaling is a requirement which is very often not needed and introducing it too early is just premature optimization.
Still, I dislike if people spread false information. Rails can scale to a certain (limited) degree but it never was easy, just the deployment then without Docker was a big mess (I didn't know one Rails guys who could deploy anything without Heroku).