Without the Harrier the UK would have had to stick with proper carriers with Phantoms and Buccaneers. The would have changed the Falklands War a bit.
IIRC, the 'proper carriers' and their associated Phantoms, Buccaneers, Gannets, etc, were going regardless, with the Harrier offering the Admiralty a handy way of keeping the fixed-wing combat aviation it was otherwise going to lose.
I'd suggest that without the Harrier, there would have been no UK carrier capability in 1982.
But 'world changing'? Not really.