I totally agree that app performance is important.
But I really think there is a difference between framework/programming language performance and acceptance-level app performance.
It is possible to have a good performance app (Github, Shopify ) even if you don't believe that Ruby is good enough in this category.
- https://blog.codinghorror.com/performance-is-a-feature/
- http://www.nicolas-hahn.com/python/go/rust/programming/2019/...