That's definitely been my experience. I work with a lot of weird code bases that have never been public facing and AI has horrible responses for that stuff.

As soon as I tried to make a todomvc it started working great but I wonder how much value that really brings to the table.

It's great for me though. I can finally make a todomvc tailored to my specific needs.

I'm not sure what sorts of weird codebases you're working with but I recently saw Claude programming well on a Lambda MOO -- weirder than that?