Generally I agree, but an entrepreneur who walks into a VC pitch with execution at least partially accomplished should feel confident they're not going to get their idea stolen.
If you don't have enough execution under your belt that you have to worry about your idea being stolen, you aren't in a good position to be pitching VCs. That worry is a sign you should bootstrap more.
Your value proposition as a founder should never be as minimal as "It's my idea".
Your value proposition as a founder should never be as minimal as "It's my idea".