Ronaldo doesn't have the speed he had 3 or 4 years ago, but his technical capacity and football knowledge are still the same. Even if his speed and performance decline, his technical skills will never disappear.
Before his unfortunate injury he was a wing forward. After the injury he turned into a striker. Now, by playing as a target striker, he can have the luxury of spending less effort. In this way, I think he can play football for a few more years with his technical capacity and football knowledge.
Apart from that, what I see is that Ronaldo's current performance can be said to be still very good. Yes, even though Ronaldo's speed is currently decreasing. However, Ronaldo still has many good skills, such as his passing which is still very accurate, his kicks which are still hard and accurate, and his dribbling skills which are still quite good. So for now the reduced speed is not an obstacle for Ronaldo to continue playing football well. And it's true, friend, currently Ronaldo is indeed suitable as a striker. This is because Ronaldo has a tall body, excellent ability to score goals and can save more energy.