The ticket has subtle errors in its description that are only caught by someone experienced with the codebase.

The code hides an exception behind an if-then-else that defaults to the most common state, which isn't caught until it breaks things for the 1% of users who don't have that state.

The new feature quietly breaks a feature not covered by the acceptance tests.

The documentation is four times as long and nobody who relies on it can read it.

And I'm stuck spending my time going over tickets with a fine-toothed comb, reviewing PRs, and mentoring contributors to prevent all of this garbage from ending up in the live code.