Arda need to wait until the senior player gone and this might not happen in near future.
If you wait for senior players to leave, maybe Arda Guller will get bored,

but he can't displace senior players.
Unless there's a team want to buy out Rodrygo with an insane fees, there's no way for Real Madrid to sell Vinicius or Mbappe.
The crazier thing I know about Rodrygo is that he has an unreasonable clause, so no club would dare to redeem him.
Premier League is the most competitive team too, if he play for Bournemouth, he will know the struggle to play in mediocre team, which could force him to improve. This also make him able to appreciate Real Madrid, since in Real Madrid all of the players are high quality.
Maybe going to the Premier League might be better for Arda because he will be forced to continue to develop and play a lot of minutes then improve his performance.