Ancelotti career was truly saved by young players from the academy. Without Gonzalo Garcia's goal, Madrid would probably have been far from the Copa del Rey trophy. Now that they have qualified, it doesn't mean the journey is getting easier, because Atletico Madrid is ready to be a nightmare if Madrid fails to win.
Imo, Ancelotti trust in academy players must be increased, the proof is now Brahim Diaz performed brilliantly against Leganes and Gonzalo Garcia goal contribution should have made Ancelotti aware to give more space to academy players.
It is indeed time for Ancelotti to have more trust in Real Madrid's academy players this season because after all they can also contribute quite well to save Real Madrid in any competition and that has been proven as you said. But in the next match in the Copa Del Rey, of course Real Madrid must develop more in terms of their defense and attack because Atletico Madrid is a much tougher opponent than the Leganes team that was defeated by Madrid yesterday.