I think you misunderstand. Yes the president comes in with an agenda, and what we’ve seen with Reagans and such is that he’s got key people in the senate and house they work with to create legislation and get it through both chambers. Not necessarily already having the entire thing written and then just saying ‘pass this’. The executive doesn’t get to be the legislative branch. They have to work together. It also gets the needed ‘buy in’ from key people in the legislature to push for it for the president.
I am not suggesting that the Executive Branch also be the Legislative Branch. But I am saying that the Executive Branch should submit its own bills if it wants to initiate its own policies. The Legislature reserves the right to change and return for Presidential approval or outright reject those policies. When you allow 535 legislators to initiate policy, you are asking for trouble (See: Boland Amendments).
btw, I dig your nick. I listened to Johnny Rivers when I was a kid. Are you familiar with the song "Use the Power"?