I do agree with you, but saying "I adhere to the ideas of clear goal-setting, team communication, autonomy, and iterative development" doesn't lead you anywhere

I do agree with you, but saying "I adhere to the ideas of clear goal-setting, team communication, autonomy, and iterative development" doesn't lead you anywhere: you need tools and actual processes to convert this adhesion to an idea into the materialization of this idea. And that's where those companies intervene: they build an implementation of those ideas. The implementation is not adapted for any project and team and it is lossy regarding the original principles, but it has the advantage of having being seriously thought about, tested and scalable.