Yes, and they were wrong for any meaningful sample of websites. You can point to ugly yet hugely successful websites but that ignores the millions of ugly, failed websites that have long since stopped serving visitors. And equally, there are examples of beautiful sites that work and beautiful sites that didn't.

How good a website looks has a short term impact on how it's perceived, but great content (where "content" has a lot of different meanings) is always more important. That's true regardless of how much effort you spend on design.