Ruby Rails is still the best for SaaS type of product, in the West or the East. With SaaS, your cost of scaling is proportional to your revenue. That is why you see BaseCamp, Shopify, ZenDesk, AirBnB, Github. All of them works well because the cost of framework or languages shouldn't really matter, since every user are paying you. But in a freemium model or ads based model, which is extremely popular in the East, your initial breakeven point will be a lot higher.

But it is not about the technical challenges, there are very little Ruby talent pool in China. Many Rubyist couldn't find jobs and switched to Java or Python. The phase for many Rubyist is; I love Ruby, but Ruby doesn't feed me. And precisely because Ruby Rails is more expensive to run for those in charge, they will adopt something faster like Go. ( Something like Gitea [1] came from China) Which means even less project being done on Ruby, and even less Jobs, with no demand in Jobs also mean people are not going to learn it. It is a vicious cycle.

And without a talent pool, it doesn't really matter what languages or framework you love or thinks works best.

[1] https://gitea.io/en-us/