Not really true. There's a reason why the A-10 is still flying and the Harrier is not.
> The U.S. Marine Corps has extended the retirement date of its AV-8B Harrier IIs in increments until 2030, and most of the fleet will remain active through 2027, according to Boeing, which supports the 1980s-generation strike aircraft. Harriers were originally scheduled for retirement in 2015.
Harrier introduced 1969
A-10 introduced 1977
Harrier II introduced 1985.
No, STOVL is the only way to deliver CAS from the combination of improvised forward ground bases and small-deck carriers that the Marines want to their air elements to operate from to keep up with the rest of the Marine force.
Fixed wing, non-STOVL jets (like the A-10) are fine for CAS, but require different basing infrastructure that isn't consistent with USMC operating needs, hence the AV-8B and the requirements for the F-35B.
CAS requires low airspeeds as well, which is a major benefit of STOVL aircraft, which can have arbitrarily low airspeeds on account of their hover capability.