Nothing is impossible, and the hope of becoming a regular in the team is every player's dream. What is needed is to continue training and be able to deliver what the coach wants when given the opportunity. Thus, Rodrygo will gradually get his chance. However, if he wants to move to another club, it is also a good option so that Rodrygo can get the chance to play as a starter. However, the problem is, as you mentioned, Real Madrid themselves set a very high price for clubs interested in signing him. Even Arsenal were reportedly interested in Rodrygo, but ultimately they abandoned their pursuit.
The only way Rodrygo can do this is to give his best performance when given the opportunity by Alonso. If he can make a bigger difference when given the opportunity, perhaps Alonso will start considering him as a first-team player. But if the results are the opposite, he will certainly remain a substitute at Real Madrid, so Rodrygo must make the most of this opportunity and take it very seriously to prove himself as the best on the Real Madrid team. However, it is clearly not easy for every player because in the Real Madrid team there are also other best players in every line.