Real Madrid are used to winning trophies almost every season, and Ancelotti was sacked as Real Madrid head coach because he failed to win a trophy for Real Madrid last season. Real Madrid management hired Xabi Alonso so that Xabi Alonso could lead Real Madrid back to their glory days, but after Real Madrid played Osasuna in their opening match this season, Real Madrid fans weren't satisfied with Real Madrid's performance, and they criticized Xabi Alonso so that he can seat up and perform better in Real Madrid's upcoming matches.
Why are they dissatisfied? It doesn't make sense for a team to win and still be dissatisfied. I don't think those criticizing are Real Madrid fans. If they were, they would have watched the match against Osasuna. Just look at what Osasuna did: two shots without a single one on target. Just look at what Real Madrid did. They attacked aggressively.
It's only been one match, and Xabi has shown that Madrid can thrive under his leadership. Just wait a little longer for the players to better integrate with Xabi tactics and for Xabi to deliver Real Madrid the title they've been promised.