Maybe it is language specific? Maybe LLMs have a lot of good JavaScript/TypeScript samples for training and it works for those devs (e.g. me). I heard that Scala devs have problems with LLMs writing code too. I am puzzled by good devs not managing to get LLM work for them.
I think LLMs have a hard time with large code bases (obviously so do devs).
A giant monorepo would be a bad fit for an LLM IMO.