I am sure Xabi Alonso can give his best even though in his first season he fails to bring Real Madrid to win the Champions League because it does take time to change the team according to the playing pattern that he expects.
He's getting acquainted with the players gradually and also has little time to train against their next debut on Wednesday playing AI Hilal. After the match it'll be easier to speculate what the future holds for the new Coach. You can't be sure if he'd not lift the champions league at first glance. Arne slot won the EPL in his first season with Liverpool, so anything can happen if Alonso's strategy proves effective he'd come out a champion.
Not only Arne Slot who managed to present the EPL trophy for Liverpool, but in La Liga Hansi Flick also did the same thing and even more amazingly because in addition to successfully presenting the La Liga trophy, he also managed to present the Copa del Rey and Spanish Super Cup trophies.
And a little back, Xabi Alonso was the coach who managed to silence Bayer Munich's dominance by successfully bringing Leverkusen to become Bundesliga champions for the first time, which coincidentally at that time Bayern Munich was still under the guidance of Hansi Flick. Therefore, I think in La Liga, with a different club, it is not impossible that Xabi Alonso will be able to silence Hansi Flick again and bring Real Madrid back to its throne.