You sign a contract to commit to not selling the company's intellectual property, not to check your brain at the door. It's not a commitment to knowingly follow practices that will lead to failure.
I've joined companies as a programmer and seen people doing things that I knew weren't going to work. I'd bring it to their attention. Most would get all frosty about it, some would listen. Sometimes I'd be the sacrificial lamb to protect the manager who'd made the bad decisions (twice; you'd think he'd have learned the first time). On several occasions, however, they'd listen to me and examine my position in terms of its technical merits instead of in terms of seniority at the company.
Fealty is for feudal societies. When I went to work my experience came with me. If they want a tabula rasa they can hire an H1-B.