I don't think vegan activism is useful at all. At least not the kind that follows the laws of the human supremacist systems we live under - and even then, while effective for a select few individuals, I do not see change coming out of those.
There is no path towards a vegan world to be taken, the best thing to hope for is the utter destruction of all regimes, and the annihilation of human supremacy one way or another. Which is something no individual can bring about, and it probably won't happen for centuries, so it's moot.
Might as well make your own reality and surroundings the best they can be. There is naught left to do for us.