Isolationist country that thinks they are better than everyone due to being technologically more advanced, spiritually more advanced (to them), more progressive and blessed by a God.
Plus, usually when they see foreigners, they are trying to take Wakanda's shit and kill Wakandans.
BUT...
It isn't "hate." It is superiority and being distrustful. They don't trust outsiders completely. But they don't HATE them. You earn their trust and they welcome you like any other Wakandan. Numerous non Wakandan's have walked into Wakanda without being hated. Hell, they have a school now that accepts outsiders.
Ramonda, for instance, isn't Wakandan. And they respect the hell out of the Queen Mother.
X-men writesr are simply trash and don't care about the mythos enough. it is why Storm should go away and Nezho should go die somewhere tragically.