I think even T'Challa's dad was on board with the "Wakanda first screw everyone else" mentality.
But certainly T'Challa himself was different. That's the thing that seperates him from the rest... he wasn't just a king. He was a super hero. And in the end, for better or for worse when push came to shove he acted like the former rather than the later.
Still, I do think that sort of mentality makes sense. Not to the degree of the universe burning per say... but doing what it takes to protect your people. Not saying I necessarily agree, but I understand it. It makes sense. If the rest of the world needs to sacrifice Wakanda to protect itself, they will. It's not nice, but if that's what they need to do then they're going to do it.
Course, that applies to the non super hero world, who realistically wouldn't be able to do jack against Thanos even if they tried. I would still assume super heroes (the Illuminati at least) would have tried to stop Thanos unless they were unable to for whatever reason.