I will give you other Ronaldo as other example. I am from old era, so I better know this Ronaldo.
Old Era Ronaldo wasn't so fit towards the end of his career at Real Madrid, for example. I remember he would get criticised at Real Madrid for being overweight and had poor form at times. That was between 2005 and 2007 if I recall well.
Even if you have a very good skill, if you don't have good body physique and not fit enough, it will affect the way you play especially at top level and end up warming the bench. Look at what happened to Hazard.
Hazard was not always the most professional guy in his career but he also just got a lot of injuries, which is one of the reasons he retired. People are saying that Luis Suarez is old and while that is true and he will not be as good as he once was, the soccer competition in US is still on a lower level than compared to Europe, so he can still make a (huge) impact.
I don't understand how an active footballer can become obese because they have to train so much, run so much and so on. They burn tons of calories every day and even if they drink soda and eat some junkfood, they still won't be able to put on much weight.
Hazard was a very good player all the time, it's very pity that he retired very early from football. By the way, Luis Suarez transfer in Inter Miami is because of Messi's influence. He wanted to keep in FC Barca too but was unable to do that. Now, he managed to play along with Suarez in Inter Miami but I have seen articles where Luis Suarez says that he has a tremendous pain and every day is a nightmare for him, he takes pills and injections before he plays football. He said that it's so painful for him that he can't play with his kids, so, I don't know why he doesn't retire.