Nobody wanting to play Vanguards isn't rocket science.

They took a bunch of powerhouses from Marvel and made them bad on purpose. They've got massively restricted damage, movement and ability expression, and they were made completely dependent on supports.

That's it. There is NO mystery. There is no "solution" to making people want to play them, beyond making them no longer be terrible shells of the characters they represent.

So either you want them fixed or you're OK with nobody wanting to play them. Pick your lane.