Chess is dominated by young players because, apart from the brain, no part of the body is actually involved. It's true that you need to have a healthy and fit body to focus hard on the game, but technically your brain is the only party involved. Going from one tournament to another is exhausting. Younger players recover faster and can effectively participate in more tournaments.
And for the few most important players in the world, the effects of aging on your chess game are inexorable, it's true. If you've enjoyed a friendly game of chess from time to time, getting older is no reason to stop playing. I think it's useful to compare and contrast the situation with another mental game, Go, in which, unlike chess, a Go player would never dream of training against a computer. My personal speculation is that of the younger generation, only Magnus Carlsen and perhaps Caruana have realized the importance of human interaction in maximizing chess potential.
The gradual deterioration of the skills of older players also keeps things fresh in the field of competitive chess. My interpretation of the data leads me more to wonder why two generations (I think a chess generation is about a decade old) of chess players have been so terrible, with the exception of Magnus Carlsen. This may be the reason why, after an exhausting game of chess or a long day of studying, you feel so tired and exhausted. In addition, the analysis does not take into account possible human outliers, such as any player who does not continue to play chess after a certain age, or other possible trend disturbances.
Because of this, chess actually depends on a healthy body more than most people realize, and the effects of aging on the body can be translated into the brain, which in turn comes to light on the chessboard. The unique thing about this particular study was that it pointed out the obvious bias that many previous studies had when it came to studying the results of older chess players once you mention it. Aronian and Spassky even seem similar to me in their tastes towards the West and in living parts of their chess careers in the West.