I think so too, and I believe it's due to the numerous injuries, but Xabi Alonso won't be able to make Real Madrid much stronger in his first season. Xabi Alonso isn't a coach with experience in major competitions with high pressure, so that will have a significant impact.
In the Champions League, everything will be different. The competition for the title is quite fierce because every team is ambitious to win the UCL. I think that's the reason.
Xabi Alonso may not have much experience in major competitions, but his success at Leverkusen didn't come easily because it required extensive preparation. The Bundesliga is also quite competitive, and leading Leverkusen to the Bundesliga title was a remarkable effort. I'm confident Xabi Alonso will be able to lead Real Madrid back to the top, but he needs to consider the number of players he needs in defense.
If we look at Real Madrid's weaknesses we can say that the defense is a crucial position, and without a thorough evaluation, it will become a problem. Injuries to players can have a significant impact so Real Madrid needs to consider other options, such as recruiting additional players for that position.