It's a problem right now for code that isn't being read by humans.

LLM-backed agents start by writing slightly bad code that's a little too verbose, too careful in error handling, writes too much fallback code, among other common minor LLM-ish flaws. And then it's next turn of the crank sees all that, both as an example but also as code it must maintain, and is slightly more bad in all those ways.

This is why vibing ends up so bad. It keeps producing code that does what you asked for a fairly long time, so you can get a long way vibing. By the time you hit a brick wall it will have been writing very bad code for a long while, and it's not clear that it's easier to fix it than start over and try not to accept any amount of slop.