That's overrating old time fighters who fought in much worse eras when the sport was less developed. The only eras that are clearly better than the 80s is the 90s and 70s. He's not the greatest of all time but the likes of Jack Johnson, Jeffries, Corbett, Langford, Wills, Dempsey, Tunney, Patterson, Marciano, Walcott, Charles, Willard, Schmelling, Baer would get absolutely mauled by Tyson and most of them probably inside a single round. I'd also pick him over Louis, Frazier and Liston too. Foreman is a toss up either way going by Foreman-Lyle. Ali likely beats him, but stylistically Ali is open to the left hook. For me Cus De Amato designed Tyson's style to pick apart the likes of Ali and Holmes. Prime Holmes v Prime Tyson is hard to call. Wlad could beat him on points or lose by KO, almost a toss up. I think Vitali beats Tyson by decision because of his range, height and workrate. Holyfield I think always beats Tyson. A Bowe fight would be interesting, Bowe is much bigger with great workrate and agility for a man his size. But Bowe never faced a puncher like Tyson and had a leaky defense, arguably no defense at times. Lennox probably beats him 8 out of 10 times, Lennox didn't beat a prime Tyson though.
Out of today's fighters he'd obliterate AJ, Fury I think beats him by decision. Usyk is a toss up, because Tyson is faster than Usyk and much better inside. It would be either Tyson in the first 6 or Usyk by decision. But if Fury can stun Usyk, Tyson can level him.
You complain about Spinks being a LHW but most pre Ali champions were the same size or smaller with the occasional big clumsy oath along the way. Also while Holmes and Spinks are the only Hall of Fame fighters, allot of people had Carl Williams beating Holmes before Spinks did.
I'll add that characterising Tyson as overpowering opponents with speed and power is short sighted. It's somewhat true but he overwhelmed opponents with defence and skill too. Arguably the most skilled heavyweight of all time. In the 80s he had the stamina to outbox opponents over 12 rounds too. It was only post prison that he didn't really have the stamina in the late rounds