With 12-year-old GMs running around it's hard to know how long.
But still, chess is a game that favours young people that have more energy and can calculate more, and that peak is achieved in one's late teens.
Fischer lived in New York, and therefore could play in the Manhattan Chess Club.
One other factor is that 3500-level chess engines are freely available for anyone with the net to analyze every situation, every move.
And then there are the streamers like Hikaru who teach chess so brilliantly. He is a true one-off, to be that top-level and able to live-comment his own blitz games. It is an underappreciated and completely unique talent, and enlightening for the chess afficianado.