It's very difficult to keep fit for a man of any age, there's a difference between regular physical fitness and the hardcore sculpting of the body; a serious business of body and muscle-molding that Arnold Schwarzenegger used to do back in the day.
For many, he had been a standard and still Is.
However, it should be noteworthy that this is not an everyday human body, it involved regimented drills that no professional athlete in the world would naturally undertake; bodybuilding is a lifestyle, and attaining the type of physique that Arnold possessed during his younger days only comes from a very specific type of workout that is designed not necessarily to increase strength but to produce a very specific appearance. These types of workouts strip away as much fat as possible and grow the size of the muscles to sometimes an absurd degree. The results can be impressive, but it does not provide as much strength as you might think, and it fades once you stop doing the intense training and dieting required to maintain that appearance.
Daily workouts will give you a fitter-looking physique that comes with stamina, but aesthetics are not guaranteed and should not be your goal because many athletes, such as weight lifters, do not look aesthetically pleasing to the eyes. You could get a stone-cut kind of body if you were training to fight MMA. However, it would be absurd to assert that one is unfit because of a big, hefty, or possibly slender frame. One might confirm that, in a fair fight, Arnold would not have been able to compete with Eddie Hall in a strength test
Certain types of natural physiques are more attainable to most people. You could look a lot worse than some other guys and your doctor would still say you were physically fit. Physical fitness comes in many forms. Just because someone isn't a sculpted bodybuilder doesn't mean they aren't fit.
Imagine, Arnold who is almost hitting a century old now, even if he wanted to do his old bodybuilder routines it probably wouldn't be near impossible and unsafe for him at his age. And I'm quite sure he doesn't want to go back to that even if he could. He doesn't need to prove himself like that anymore.
Sadly, most of the people on the planet will never be in as good of shape in their entire lives.