Howe, Orr and Gretzky were lucky enough to shoot at this for their careers. Yes, they were that much better than their peers at the time, but Jagr is the only player to successfully transition with the game.
Gretzky was still dominate as a 38 year old in the dead puck era, the NHL was nothing like it was in the 80s yet he still put up great numbers. Lemieux played fine hockey as an old broken down man into the start of the Crosby era. Many players have had great careers spanning over different eras, take Patrick Roy for example, an elite goalie in the 80s, 90s, and 2000s. Jagr is far from the only one.
And alot of people who dont seem to grasp how bad the next guy infact was. Of course Orr is way above Karlsson but cant really judge them by the same metrics cause the level of play was beer-leagueesque back then compared to now.
There was an immense amount of talent in those days, even if they approached the game differently. I personally wouldn't call the Canadian or Russian summit series teams a bunch of beer leaguers. People immediately assume players today are miles better than players in the past. Sure players work out more and have better conditioning, have better equipment, coaching, and so on, but also take into consideration that the league is way more watered down today, with fewer super stars and way more plugs. If anything today's NHL is more grinder friendly than in the past.
The Montreal Canadiens used to look like all star teams, with a good dozen superstars, whereas today teams are lucky to have 2 or 3. I don't have the numbers in front of me, but I believe the pool of players was wider in the 70s and 80s because more people played the game back then, and hockey was a much more dominant part of Canadian culture. Yes Karlsson is very good, one of the better offensive defensemen in history, but he's far from GOAT status, and people that seem to argue along those lines appear to me to have little knowledge of the history of hockey and the famous defensemen that revolutionized and dominated the game to a much greater degree before Karlsson.