It's only tennis, really.
In the NHL, Connor McDavid is the best player in the league, and there are many others. Matthews, Marner, Gaudreau, Mackinnon, Point.
And Mahomes is a phenom. He most likely just got screwed by a coin toss if truth be told, and Brady's great obviously, but so are the Patriots as a whole. It's not like he does it alone. Plus, look closer at the Rams and Jared Goff. Not as good as Mahomes, but he's not bad.
The MLB has a bunch of young talent. The Red Sox and Astros alone are loaded with it, and the Yankees aren't far behind. A guy like Machado has been great for a long time too, and that guy Hader that came out of the bullpen for the Brewers this year was lights out. Cody Bellinger is pretty good too. Hasn't done jack in the playoffs, I admit, but he was Rookie of the Year.
I see metsman already mentioned some NBA stars too, so really it's only tennis that has this "problem" for lack of a better word, and we've been through this a million times where tennis is concerned. Some of it is advances in tech, allowing the older generation to be able to play awesome for longer, some of it is homogeneous court surfaces, most of it is just lack of talent in comparison to Djokovic, Nadal, and Federer.