I wouldn't say proven or disproven, as much as it became no longer applicable.

The world he was modeling in the 18th century is a very different world than we ended up getting. IMO it's neither right nor wrong, it's just a reasonable observation that made sense for the time.

It's somewhat analogous to Y2K, in that there were obvious problems that were going to happen. We didn't experience those negative outcomes because immense engineering effort solved the underlying problem. That doesn't mean Y2K was "invalid" or "wrong," just that the problem itself got addressed before it could blow up. Same with Malthus, chemistry and mechanization allowed us to solve the underlying issue of food production scaling slower than population growth.