Waterfall is a great methodology where warranted. It ensures you're doing things in a principled, predictable, repeatable manner. We see all this stuff lamenting about and trying to implement reproducibility in science and build systems, yet seem to embrace chaos in certain types of engineering practices.

We largely used waterfall in GEOINT and I think it was a great match and our processes started to break down and fail when the government started to insist we embrace Agile methodologies to emulate commercial best practices. Software capabilities of ground processing systems are at least somewhat intrinsically coupled to the hardware capabilities of the sensor platforms, and those are known and planned years in advance and effectively immutable once a vehicle is in orbit. The algorithmic capabilities are largely dictated by physics, not by user feedback When user feedback is critical, i.e. UI components, by all means, be Agile. But if you're developing something like the control software for a thruster system, and the physical capabilities and limitations of the thruster system are known in advance and not subject to user feedback, use waterfall. You have hard requirements, so don't pretend you don't.