It's underrated how tough it can be to get a new thing off the ground, and how delicate that phase is.
If a solution is optimized for getting to scale, and not for getting started, it might just be the wrong solution for getting to scale. Hopefully everything we use is capable of the scale we may eventually need of it, but that process will be a windy journey, and you can't even take the first step if you're stuck at the starting gate.
When AirBnB was figuring out what it was, trying new things, running Craigslist adds to try and get customers, Rails was there with some basic ways to provide models, views and controllers. It was opinionated, and ready for the challenge.
For no specific API or pattern or technical solution, I'm still a very excited Ruby on Rails developer. I also love a hypothetical scenario where Forem is eventually rewritten in some kind of way where we can package the whole thing into a tight, radically memory efficient binary. But for now, and probably forever, we're still riding the Rails.