For me the biggest gaps in LLM code are:

- it adds superfluous logic that is assumed but isn’t necessary

- as a result the code is more complex, verbose, harder to follow

- it doesn’t quite match the domain because it makes a bunch of assumptions that aren’t true in this particular domain

They’re things that can often be missed in a first pass look at the code but end up adding a lot of accidental complexity that bites you later.

When reading an unfamiliar code base we tend to assume that a certain bit of logic is there for a good reason, and that helps you understand what the system is trying to do. With generative codebases we can’t really assume that anymore unless the code has been thoroughly audited/reviewed/rewritten, at which point I find it’s easier to just write the code myself.

This has been my experience as well. But, these are things we developers care about.

Coding aside, LLM's aren't very good at following nice practices in general unless explicitly prompted to. For example if you ask an LLM to create an error modal box from scratch, will it also implement the ability to select the text, or being able to ctrl c to copy the text, or perhaps a copy message button? Maybe this is a bad example, but they usually don't do things like this unless you explicitly ask them to. I don't personally care too much about this, but I think it's noteworthy in the context of lay people using LLM's to vibe code.

I've seen a lot of examples where it fails to take advantage of previous work and rewrites functionality from scratch.