Making rules sounds awfully like legislation, which is a job for the legislature rather than the executive. Arguably, the executive can only regulate the executive, and Congress has to pass laws which apply to the populace at large.
That’s certainly not the way things have been run for a long time, but it doesn’t seem irrational to argue that’s the proper constitutional structure.
The legislature is well within its rights to delegate rulemaking authority. (I recognize that non-delegation is a live debate, but I think it's a silly one.) But the executive has to make those rules within the bounds of the delegated authority.
Article I, Section I states ‘All legislative Powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives’; it says nothing about delegating those powers to independent agencies or to executive agencies. None of Congress’s enumerated powers state or imply that it may delegate its power to anyone else.
It would be pretty surprising if a law passed by Congress delegating to Charles Windsor its power to write the laws about taxes, borrowing money on the credit of the United States, regulating international and interstate commerce and so forth were constitutional.
> None of Congress’s enumerated powers state or imply that it may delegate its power to anyone else.
That may be what you believe, and there's been a lot of debate over that, but courts have time and time again ruled that the legislature can delegate power. Maybe current SCOTUS will reverse a lot of that, but that remains to be seen.
That’s certainly not the way things have been run for a long time, but it doesn’t seem irrational to argue that’s the proper constitutional structure.