The problem isn't the warnings. The problem is that every damn website where you read a single article thinks it's somehow ok to set a cookie (and track you).
The problem is both. We can't pretend that failed solutions with good intentions are not problems. It is not worth adding more problems on the stack because the guess-and-check solution whims fail. Solutions can be measured and worked towards, not guessed at where they do such large changes that their failure is also large.