I'm not sure you could of made a worse point if you tried, to be honest.

Modern Rails is plenty quick (Ruby + Falcon is 2X faster than Python Async) and is incredibly ergonomic for LLMs as a codebase.

The tooling is also incredibly strong, with 200k~ Ruby gems in the ecosystem.

But ultimately, none of this matters. You can use any framework/language now and the LLMs can be productive on them all. Tools missing? Astra one shots it.

If you get to the scale where milliseconds result in $MM bills, then you port with another prompt, or just point more tokens at the bottleneck.