The Merengues went to the Etihad originally looking for a draw. Cristiano Ronaldo was out injured and no one could blame them for thinking "drawing away without our best player isn't too bad," because they were right. A draw was good and they are happy with it.
The problem is the Citizens looked as content to tie. Even at home, they rarely sent players forward and Keylor Navas was kind of chilling all match. Losing David Silva to injury in the first 30 minutes didn't help, nor did Yaya Toure being out, but Sergio Aguero and Kevin De Bruyne are great. And we barely saw them. Defensive discipline and managing the pace of the match took precedence, attack neutering be damed.
Real Madrid weren't short on great players either. Gareth Bale, Karim Benzema and Luka Modric give them plenty of firepower, even if they had to deal with Toni Kroos mimicking a turnstile. Basically, it makes sense that Ronaldo and Toure's absences would hurt the teams, but they weren't supposed to turn the match into a turd.