I would have known that laminate cannot be laid directly on the floorboards. So all the work was for nothing and now it has to be relaid. But also on a proper subfloor.
Mistakes are there to be made. No one was born a craftsman, that's just how it is. Most of us have already made mistakes, and I have too. I have also laid laminate flooring and simply forgot the vapor barrier. When I was almost finished, I then noticed it.
Sure, no one is immune to mistakes. It just happens. The thing with the vapor barrier is of course annoying and that means having to lift all the laminate again. I wouldn’t do without a vapor barrier on the ground floor. The basement is often not heated and moisture can form there.