To clarify, he didn't say they're the only 4 that could play, but that they're the only 4 that could be "nearly as successful".
It is mostly nonsense, but I'd say he's at least partly right about guys like D-Wade, who would get handchecked on the perimeter, bodied up on the drive, and thrown down at the rim a lot more often back in the day. The slashing and driving game was a whole lot tougher back then without today's protections.
But yeah, it's mostly just a case of an aging guy pulling the "kids these days are soft and spoiled" routine. Same as it ever was.
EDIT: the article as a whole is a great read, though. Fascinating look at MJ, warts and all. Recommended.