alt Hacker NewsRails is slow, and it has little tooling. If it was me I would have used Go so that compiler would give the LLM some errors and narrow its error window, is way faster than Ruby and makes way more sense to have a way faster code than a slow one for the same price, everyone can read Go code and it is so narrow in the possible space of decisions that an LLM can never write usual spaghetti that it writes in other languages to save tokens... I think the problem is in looking at Rust as the alternative.
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.