you are right that young players will replace old players, this is not Ronaldo's problem why not play maybe because his performance has decreased compared to young players, old players like Ronaldo and other old players should also be aware of that and be prepared to be replaced, as before of course ronaldo used to be a young player replacing previous players who were retired and old, so i think people need to face the reality of that even though it's bitter
That would be a reasonable attitude but humans can be very unreasonable at times, what you are describing is just the way things work everywhere, with new generations taking over the older generations which in return they will be overtaken by newer generations as well, but this can be very difficult for some people to accept, in fact in other sports many star players retire before they are benched as their pride does not allow them to accept this new reality, so either Ronaldo accepts that being benched is now a possibility at Portugal or he retires from his national team.