Slightly an extreme example, but that is what Arsene Wenger does.
He never plays for "the present". He always thinks about the future. He is obsessed with new youngsters all the time.
And even when those youngsters grow up and start to be "the present", he doesn't stick with them but then again makes a mistake and forces some new, even younger players for the future.
If our coaches would listen advices from fans from this forum, we wouldn't be much stronger than Arsenal with Mats, Bartra, Montoya, Rafinha, Munir, Sandro and Deulofeu in the team.
What is worse, in 2-3 Seasons, fans would ask for even younger, new gems to be in the lineup.
Again, this is why Arsenal doesn't win titles, and we do.
And yes, we should play some younger players, but you can't risk the present because of the future too much.