The thing is, if you boycott twitter or facebook, you don’t get to be on those platforms anymore. That’s a cost. But if you boycott #PatreonExodus, it doesn’t cost anything. In fact you save money! There’s no barrier to leaving for the subscribers.
For the creators who provide the content and harvest the subscriptions there is of course a substantial cost, but if an alternative platform is created, there will be no barrier to switching.
It won’t suffer from the Gab curse of attracting all the racists and Nazis, because, as a Patreon subscriber you are not subjected to anyone’s rants. Your are just supporting those whom you deem worthy of support.