I've been working on and off with formal agile since 2002, and worked on "disciplined professionals" teams.

You know what is disciplined? Formalizing a process and following it, even when it's inconvenient or annoying. Getting by on talent, high bandwidth communication, and sufficiently small scope might work, but don't call it "discipline". It's luck and narrowly defined circumstance.

Try using that method on a $50M enterprise project with 100+ developers and see how far you get before you choke to death.