Not really.
Island populations are always an exception. Genetic diversity helps with unexpected new situations like foreign species or diseases. Those aren't a factor in island populations. They have no incentive to diversify. Still, when you introduce a new predator or other species into a closed system like an island, you can quickly see the native species getting into problems.
As for Orang-utans, they fall prey to human destruction of their habitat like many other species. Genetic diversity means little when compared to human intelligence and destructiveness. Our intellect is the great equaliser, allowing us to fly higher than birds, move faster than cheetas, feed a hundred times more of us per area than grazing animals and kill creatures far more deadly than us.