"there’s no solid indication the last war, or at least that type of war is over."
The USMC really never needed all those tanks and strike aircraft if they'd been restricted to doing what they were good at and what they were originally designed for - littoral operations, not full time war fighting onshore miles in the interior. .
The Army and Air Force could easily have handled every big fight since Inchon.
It happened because they didn't want to be seen to be sitting out the fight - mainly because they're patriots and aggressive as hell but also because if they weren't in Afghanistan etc some people would claim they were irrelevant and they'd be cut back. So they finished up as a duplicate of the USN and USAF both role & equipment-wise.
Now they're being re-oriented back to what I guess you could call "core values"