The last successful Marine Corps amphibious assault was at Inchon in September 1950. Over 71 years ago. And that was largely unopposed. The Marine Corps over the 70+ years has been that of a 2nd army, dedicated to land-based campaigns.
Even with a transition to training against potential adversaries like China, I can't see where amphibious assaults would be a future thing. China might have more need for this training, with their eyes set on Taiwan. Where would the Marines undertake amphib ops? Invading the Chinese mainland? Not likely.
Less glamorous but more likely would be garrison duties, i.e. defending allied countries from Chinese attack using local forces. And, of course, air-naval power. Vietnam, the Philipines, Thailand, Malaysia, Indonesia, etc. are all increasing their defense budgets by double digits annually. India, Japan, Australia, etc. are all also taking newly-aggressive Chinese foreign policy a lot more seriously.
Turning the Marines into a light infantry force, devoid of armor & artillery, would be an error in rehearsing for war against a conventional foe like China.