Mbappe and Vinicius are great forwards who will be the leaders of Real Madrid's attack. Rodrigo has nothing to complain about, he got the opportunity from Alonso to play from the first minutes but was substituted in the middle of the second half and Vinicius had enough time to score a goal, I think this is an indicator of how much more important Vinicius is for Real Madrid. Rodrigo wants to play but for now he cannot compete with Mbappe and Vinicius, and Garcia by the way came on as a substitute only in the 74th minute, so Alonso is giving everyone a chance to play for now.
You have been making really good points concerning forwards of Real Madrid. Vinicius and Mbappe are obviously high flying players in attack. Fact that Vinicius was off bench and scored within two minutes show how significant he can be. You are correct that Rodrygo is indeed in unfortunate situation he is excellent player but due to sheer number of stars and talent in squad he finds himself in rotation and does not have any guaranteed starts. Manner in which Ancelotti is affording opportunities to every player, including Garcia is sign that he is attempting to manage his very skillful team and have them all in shape throughout whole season.