This is consistent pattern.
Two engineers use LLM-based coding tools; one comes away with nothing but frustration, the other one gets useful results. They trade anecdotes and wonder what the other is doing that is so different.
Maybe the other person is incompetent? Maybe they chose a different tool? Maybe their codebase is very different?
There was actually a good article about this the other day which makes sense to me, it comes down to function vs form kinda: https://www.seangoedecke.com/pure-and-impure-engineering/
I would imagine it has a lot to do with the programming language and other technologies in the project. The LLMs have tons of training data on JS and React. They probably have relatively little on Erlang.