All we need is a 28th Constitutional amendment that states: The federal government is abolished.
If three-quarters of the states approve it, Washington DC seizes to exist.
Of course we would need a state’s structure to pick up the pieces and create a way to disassemble Washington and appoint a new commander in chief to take care of the military. That’s what an Article V convention would be for - to create an interim government to set up a new federal government with few and limited powers.
If that happens, and it’ll never happen, what do you imagine Washingtonians will do? Say it’s been fun, boys, pack up whatever swag is lying around, and retire to their farms like Cincinnatus? They fought our bloodiest war to keep states under their thumb. Imagine what they’d do faced with the prospect of their own elimination, as they only pretended the Civil War was about, for instance in the Gettysburg address (government blah, blah, blah the people shall not perish from the earth? Wha?)