Yes, the Harrier needs to be replaced. Do you want to use a $250,000,000 plane in Close-Air-Support?
It would make more sense to take 300 A-10s and modify them for Carrier Ops. And yes, I know how far-fetched that is.
CAS needs low/slow/tough as nails/able to absorb lots of small arms fire. That ain’t the F-35.
The thing is that the Marines need a ire that can operate from the LHDs and such. The A-10 could never be modified for that. Not sure about making them carrier capable.