I was part of a development organization that, driven by guilt and shame, tried to mature and improve their "ad-hoc" processes by fully embracing by-the-book waterfall.

To me it felt like they were saying, "You know all the things you did to make your last project a huge success: the short iterations, tight feedback loops, early and frequent customer involvement, designing your systems to accommodate change? Yeah, don't ever do any of that again."

So I left, and found that dogmatic by-the-book scrum shops can also be horrible places to work. Live and learn.