My mother's cousin retired from the Marines in the early 70s, a Master Gunnery Sgt., was in China, WW 2, Korea, and Vietnam. He hated the army in a very physical way. The reason why is because the army wanted to disband the Marine Corps and absorb it into the army. I could see similar political and operational ramifications.
The idea of disbanding them is enticing and a fun mental exercise, but it ain't gonna happen. What with not one but two TV shows, holding the public's attention, the books and movies, etc. Yes, they are largely clown shoes, but they need better leadership, more oversight, and accountability, plus limited scope of mission. But they don't pay me the big bucks to figure stuff like this out.