It was the Marine Corps who taught them the amphibious techniques we developed during the ‘20s and ‘30s under Gen. H.M. Smith AND turned them on to the Mike boats and LVTs which we ALSO developed in that time frame. But I was speaking of the modern division of labor, not the past, glorious as it is to the Corps.
The "modern era" marine corps hasn't made any major amphibious assault landings since Korea (which, by the way, involved both the 1st marine division and the 7th infantry division (army). Vertical envelopment has rendered the amphibious assault a second tier capability. While the USMC is probably still the most capable beach landing force, it is by no means the only assault force. Consider the 101st Air Assault Division, the 82nd Airborne Division, the 173rd Airborne Brigade. All are capable of kicking in the door virtually anywhere in the world, including in proximity to the beach.
Seriously, the USMC certainly is a fine LIGHT infantry organization, but the history they teach young marines is only a part of the story. Unfortunately, some people choose to ignore or minimize the rest.