I sometimes don't understand why technical people seem resistant to "lean startup" methodologies. It's just the scientific method, applied to build a product! You build hypotheses, then try to prove them, and in the course of this, usually learn more information about the world. That simple.

You think you have a product which is useful to someone? Prove it! Talk to people, ask them, build simple prototypes of the core parts.

You think you know how to sell your product? Prove it! Build out some sort of pipeline, e.g. use a landing page and see if you can get people to it.

Etc.

There are good and bad ways to do this, obviously, and it's not easy. But the basic idea is simple enough - and most of the arguments against it sound pretty much the same as how it would sound for someone to be against scientific experiments and hypothesis testing.