@Raoul
There was no unanimity on apartheid. Even in the years leading up to the liberation there was loads of political factions in the west sympathetic to to the regime. Never mind that they had many allies 1-2 decades prior.
The importance of calling the Israeli policies apartheid is to persuade people the situation is actually very similar, because they are, and that's a bad thing that needs changing.
Yes it doesn't directly improve the situation, but it may persuade people to vote for politicians who care about the issue. It's not like the entire state of Israel isn't entirely dependent on foreign support.