Usyk is considered a 'small' heavyweight by today's standards but would still tower of Tyson. Just look at what Holyfield did to Tyson.
I just do not buy that Mike Tyson was much better when he was younger. He simply was fighting bums and over the hill fighters in showcase events. If he could not finish Mitch Green, Bonecrusher Smith and James Tillis, how on earth is he going to finish Usyk? Is he going to out box him? Doubtful. Mike Tyson was like Royce Gracie, and he was good but had all the hype and a system set up to make him look good. Had he fought Holyfield, Lewis or Bowe earlier, the empire of cards likely would have come crashing down before Buster got the chance to do so. In many way Tyson was like AJ: dark skinned, muscle bound, KO specialist hype train, but did not have the skill to put him in that next level stratosphere.
Boxing, like all sports, is improving with age too and Usyk is at the forefront of that progression.