I think regardless of age, Messi is a true leader for Argentina and he can even start helping the younger players and this can be another advantage of having Messi in the team for Argentina.
I have posted this previously. Will post again - Messi has a lot to lose, and nothing to gain if he takes part in the 2026 FIFA World Cup as a player. And recently he suffered a serious ankle injury during the Copa America final (while playing against Colombia). Although Argentina won that match (as a result of a goal from Lautaro Martínez during extra time), Messi was forced out due to injury. I am not sure whether his health and fitness will allow him to play for another two years.
He is getting old and getting injured is something normal for a player at this age like him but the fact about Messi is he is trying very hard to have better performance and help his team. He is a player who played in many world cups and I think this can be a good achievement for any player to be in the good form since he gets old like Messi.
Now he can even help his team as a leader and help younger players.
Winning the 2022 World Cup was the pinnacle of the duo Messi and Di Maria. But the 2021 and 2024 Copa América rode this wave. But according to the coach, even without the duo, Argentina has life, they have already proven that they can win without the big stars.