If that was the case, Tony Twist is the greatest athlete to have ever participated in the Big-4 (NBA, NFL, MLB, NHL).
In reality, Twist was a terrible player who earned a place on the roster with his fists. He couldn't skate, shoot or pass.
Old-Time Hockey is fun, but players today are better athletes. All athletes today are in peak condition year round. If you aren't, somebody else is and will take your job. Hockey players, run, lift weights, box, wrestle. As do every athlete in every sport.
With that said, being a hockey enforcer wasn't an easy job. Somebody like Nikita Kucherov (or LeBron in the NBA) only has to keep his stats up. An enforcer knows there's one or two guys he has to fight every game. Every one of those guys wants to put your lights out. So you have to practice and study fight films so you know what your up to.