Easily said, but I doubt Ronaldo saw them as nothing games, thought with hindsight they were. Madrid ended up 3 points behind Atletico - but they dropped 7 points in their last 4 games. Ronaldo got a 90th minute equaliser in one of those games and then played only 8 minutes in the next three. There probably were matches earlier in the season he could have sat out - the Schalke second leg for example, and Liga matches where he could have come off early, but I assume at that stage it didn't feel serious.
From there on, there wasn't really a run of fixtures where you could say the matches were meaningless. He did sit out the Copa final, Dortmund second leg and a couple of Liga matches. That gave him a 3 week break between the Dortmund first leg and the Bayern semi-final - but I can't really blame him for wanting to play in a CL semi. I think in the end he played 5 of their last 12 games, including the CL semis and Final.
The comparison that appeared in Marca a few days ago was with Rafa Nadal. He didn't need a three week break from playing/training to give his knee time to recover - he had to take a three month break and then take his time getting back into action.