Ronaldo case is somewhat different from that of modric, Ronaldo was actually after perfection, to proof people wrong since they've been doing some bantering and calling him some sort of names(definitelymessi fans)... Losing a penalty doesn't have anything to do with experience, Messi have also lose penalties....no one is above mistakes and I'm sure that's not his first but in his current stage he's actually feeling overwhelmed by the social media bully and sure the mistake did cost him alot 
Coming back to modric, I still feel he makes some great impact in big games as an experience player IMO
Real Madrid have great players in the past years and the current one. The president of the club, Florentino Pérez have done his best to ensure things work fined for the club. He made best signings for the club, Cristiano Ronaldo and Luka Modric are two different players in the same club, they've played together for years and totally contributed in every season for the club. However Ronaldo exited Santiago Bernabéu because he was tasty to pick more challenges for himself which he quite made the long ranging accomplishment. Coming back to modric, I still feel he makes some great impact in big games as an experience player IMO
I don't think Ronaldo should continue to play like that. He is 39 years old and is no longer in the same form as before. He should rest and let the younger generation play and show their talent. I will not hesitate to say that I saw the Portuguese team play very well in the World Cup qualifiers with Ronaldo on the bench. I know that great pressure will be on Ronaldo's shoulders. If Portugal is eliminated, all the blame will be placed on Ronaldo. So the best thing for him to do is rest, so bad people don't make fun of him on social networks.
With Luka Modric it's different. He knows how to accept the truth. He is ready to sit on the bench at the Santiago Bernabeu to be ready to contribute to his beloved team when they need it. Luka Modric is still the mainstay of the national team. Although his physical strength is not as good as before, he is still the center of the Croatian team.