Not hard per se. While being physically healthy was obviously more of a blessing than a common possibility in the past, most had no qualms putting in the work if they knew something to be necessary or desirable. That goes for now too, albeit with a new set of obstacles.
The main problem comes with the sheer ubiquity of incentives throughout the “civilized” world to practice a sedentary and physically low-effort lifestyle. Add in the typical work schedule, and many have barely any time to exercise while still having more than the slightest margin of consistent free time, if they even have that privilege. Not saying laziness can’t be a factor, but it’s less of a trait that’s inherent to people and more so a result of what someone was taught or experienced.