The Yonko are also among the strongest figures and all they do is ruling over territories in the new world being backed up by a large crew and allies, not seeing each other for decades. Same goes for Whitebeard, who lived his life mostly as a father to his crew, avoiding most conflict, not even wanting to fight Kaido in Wano to avoid unnecessary deaths, even avoiding marines. Yet he proved himself in his fight(s) with Roger. Same goes for Mihawk. He had legendary duels with Shanks that shook the grandline, acknowledged by Whitebeard himself when talking about the legends of the past. Nothing else matters. If he didn't face Vista, it is because Mihawk deemed it unnecessary. And it's not like Mihawk is not seeking the challenge. Going as far as to train the swordsman that wants to surpass him.