but also getting any following to move anywhere else is nigh impossible
That is of course bad news for crosspromotion or promotion in general. But I can imagine reasons for that. You would have to "hit" a gamer interested in your type of games, that is coincidentally stumbling over your social media. And for itch specifically, not many people even know that itch exists. So not only do you need to hit such a gamer, you also need to hit someone willing to go to this small time game platform he never heard about. But he did hear about those discord try my game scams, so better be wary and only visit steam game pages or maybe gog or one of the others he knows.