Football era's can never be thesame you can't compare Real Madrid then and Real Madrid now Carlos Ancelotti has a better team then and everything doesn't just happened suddenly even when Jose Mourinho signed for Real Madrid it wasn't easy for him at initial time it was later he started winning tittles for Real Madrid, so i think xabi Alonso should be given time before placing judges on him if he was able to win title for Bayer 04 Leverkusen when he went to Bundesliga I believe if given time he will do more in Real Madrid, there will be little pressure in him because Real Madrid is not a small team it's always like that for a new manager I believe everywhere will be calm in due time.
Every few years, a club will regenerate and make everything look different. Even Barcelona also did the same thing but there was no competition like before when Ronaldo and Messi were still in La Liga.
Xabi Alonso or other coach who had been with Real Madrid, they would definitely undergo the process of understanding the club's structure and what Squad needed to be stronger and able to compete at the top of the standings.
Now Xabi Alonso will do the same thing as Ancelotti and all of that still takes at least one season.