I don't know how you are satisfied with Juventus' performance. Did Juventus play well in the FIFA Club World Cup? I don't think the team played well. They lost two of their four matches. Juventus won against two weak teams like Wydad and Al Ain. But Juventus lost against city and madrid. Juventus lost against City by a big margin of 5-2.
Yes, I think they played very well against Real Madrid. Especially the Juventus goalkeeper, he deserves the highest score. We have to realize that teams can't always be stable. Another condition is that it's the beginning of the season, I think the coach is experimenting a lot to find the best combination.
Against Man City yes they did perform badly, even if they should have played like when they met Real Madrid the results would have been different. I think this condition will make Juventus think a lot to improve the condition of the players. This is because the transfer season is also still open, so Juventus can still take advantage of it.