I don't think it's fair to judge Xabi now. He certainly had a tough time after the crushing defeat to Paris Saint-Germain, but it's also important to remember that the squad isn't finalized yet, and his preparation has been relatively short.
I think it would be fairer to judge him after the season starts. Yes, I know that was an official competition, but most newly appointed coaches often fail. I've seen him with his young players, and that makes me even more curious about what he'll do with a little more preparation.
Losing to PSG doesn't mean he's a bad coach, he's still one of the best coach currently and the team would bounce back from that defeat I believe that the players are training very hard against the next season and the boarding is still on the process of backing him with new signings to succeed. I trust Xabi to succeed at Real Madrid he might not win major trophies in his first season but his second season with Real Madrid wouldn't be very successful.
So, if he fails to win a title in his first season, but their performances are good, I think that's perfectly normal, so he could have a better chance in his second. Don't be too quick to judge a coach, because there's always an adaptation process, and some are quick, while others take a long time.
He's one of the young coaches who shows immense potential, so there's high hope. Moreover, his coaching career is often short, and he's already earned the trust of a major team like Real Madrid.