I agree with you. Xavi proved that you don't need star players to build a strong squad. Leverkusen's squad does not have any star players. However, they are still unbeaten in the Europa League and Bundesliga. The team is ahead of Bayern Munich in the Bundesliga.
Xabi's match strategy is excellent. Xabi has managed to create a friendly relationship between Leverkusen's players. The understanding between the players is very good. This is why Leverkusen's performance has been so strong this season. In every match we see the dominance of Leverkusen players.
Apart from what you mentioned above, I also think that if a midfielder retires, he has the talent to become a great coach because of his extensive knowledge of the game as a midfielder. I am sure that Xabi Alanso will become a great coach in the future, this has been proven with Bayern Luverkusen, he even managed to set a record for Leverkusen as a club that has never lost in the Bundesliga.
I think with his intelligence he trains a team that can be said to lack big players, especially at the end of the season he can provide trophies for the squad and Real Madrid's doors are always open for Xabi Alonso, sooner or later Madridistas will welcome him enthusiastically.