Real Madrid might really have serious difficulties in retaining their title in the CL this season. Don't you think the same?

I mean it is early I know but their game doesn't look convincing. Because in one match they look really good but in another they struggle to score a lot. Just like it happened in the Lille match. Maybe it might be Manchester City's turn after a break of 1 year. It is just an assumption but we will see.
I'm aware of another truth like Real Madrid can win a CL title in even a season they don't look fascinating. Last season was really like that. But doing this twice won't be easy at all.