To be fair, if the nutritional and training advances available to players today were available back then, Hollywood Henderson would not have been a 220 pound linebacker - his size would more resemble what you see now.
If we're gonna play this game where you try to ascribe all the benefits of the modern day to Henderson, the truth is that there are also some ugly downsides that would've made it even harder for him to thrive.
First of all, his drug problem would've been a much bigger problem in the modern era of football. Constant drug testing. Not to mention he actually hid drugs in his uniform and did them on the field during actual games. That might've flown back in the day but today with HD video all over the place and an army of Twitter detectives, he'd get busted just like the baseball pitchers who routinely get busted by random Twitter people who spot their pine tar or whatever illegal stuff they try to hide on the mound. Also, his ugliest behavior problems arguably only started after his playing days when crack popped up. Crack didn't start popping up until the early '80s, so his childhood and his whole playing career had already come and gone by the time crack became a thing. But if he'd been born in 1999 like Parsons, he'd have spent his entire life in a world where crack existed from Day 1. It's unlikely he'd have been able to function well enough to thrive at the collegiate level or make it to the NFL in the first place if he had to live his life over again but this time crack doesn't wait to be invented until after he's already retired.
Second, the guy was a creep. Didn't he get busted for giving crack to teenage girls in exchange for sex? And one of the girls was handicapped in a wheelchair?
The NFL panics and throws the book at players who embarrass them badly enough. This is a dude who would've absolutely been busted doing drugs on the field in uniform during actual games, and who was dangling drugs to force handicapped teenagers to sleep with him. Yikes. He'd have been busted and banished before he made it out of his first preseason in the NFL today. Dude was a mess.