You really do not know what you are talking about, it is not about the language, like it was repeated in this forum many many times already. We serve an application in PHP to thousands of users per second in less than 100ms constantly.
Sometimes it is the language. Or at least the ecosystem and libraries available.
My go-to example is graphql-ruby, which really chokes serializing complex object graphs (or did, it's been a while now since I've had to use it). It is pretty easy to consume 100s of ms purely on compute to serialize a complex graphql response.
I have mixed feelings about this. It's saying that python is too slow for data science ignoring that python can outsource that work to Pandas or NumPy.
For GraphQL on Rails you can avoid graphql-ruby and use Agoo[1] instead so that that work is outsourced to C. So in practice it's not a problem.
