The struggle in India was for the (bourgeois) democratic demand of independence from the British Empire. This was successful. The struggle in South Africa was for one person, one vote. This was successful. The black masses of South Africa *are* better off, in so far as they now have a vote, and elect a government, which they didn't used to be able to do.
Of course they're still oppressed by capitalism. Of course they now have new (actually, quite a lot of the old) capitalist oppressors. But to confuse class oppression with the issues of democracy (yes, bourgeois democracy), for which they were fighting is not helpful.
It certainly is not what Trotsky was doing in the theory of permanent revolution.
There were issues of socialist democracy posed by the struggle against apartheid, for instance. But to raise them, and fight for socialist - or workers' - democracy, did not mean saying that the issues of bourgeois democracy - one person, one vote, an end to racist laws, etc - were not worth fighting for, or that to win those struggles would be empty and meaningless.