I'm not surprised.
Ayton is a really good player. The fact that he could be even better is the problem not because, gee, it would be nice if he were better, but because of the message it sends to his teammates. You can't have a culture of everyone working their hardest and then one guy strolls in at 80%, does his part, and then wanders off to play video games. He's not honoring the effort of his teammates, and that means that, over time, they will either resent him or stop working so hard themselves.
You see the opposite when a team's best offensive player works very hard on defense, or dives to the floor for a loose ball. They could be a very good player without doing those things, but they make a statement: If I'm doing everything I can to help us win, then you sure better fall in line.
In terms of personality, Ayton is similar to Shaquille O'Neal. O'Neal was so much the better player that he could be an all-time great without ever being much of a defender or learning to shoot free throws. But when the Lakers had their rocky stretches, which was often, it was typically because Bryant and O'Neal's other teammates were fed up with O'Neal's reluctance to work hard. But, he was a great player in spite of that, and the rest of the roster was talented enough to win titles even without their star center's full effort.
If the Suns had more elite talent around Ayton, his problems would be less magnified. But it's a roster of over-achievers, and that's exhausting to keep up over a long season. To keep that energy going, you need to be inspired by a culture of everyone doing it.