Why are so many people saying that if some developers write bad unit tests, then all unit tests are pointless and a waste of time? Yes, I've seen thousand line

Why are so many people saying that if some developers write bad unit tests, then all unit tests are pointless and a waste of time? Yes, I've seen thousand line files of boilerplate unittests that don't actually say anything useful about the system. I've also written unit tests that tell me in 2 minutes rather than in 3 weeks that somebody has broken my code. If your standard for a system of testing is that it guarantees that people can only write good code, you're insane.