I think I was clear enough. I doubt that he intends to play on a highest level at that stage. If he wants, he can play until 40 and still contribute.Not a given unlike Dembele? Messi's work rate has always been very poor compared to other players. For years he's been clocking under 10km per game which is on average about 2km less than other players.
Even though he declines he'll still be a better player than probably every other player mentioned in this thread.
His workrate was much better and he was a part of Pep's ultimate pressing system. Its decline isn't the reason behind his hypothetical absence in the World XI but rather a symptom that allows me to assume that he can retire/quit highly competitive football early