While Luka hasn't been in ideal playing shape for some time now, it's not that unusual for the weight/conditioning of an NBA star to fluctuate a bit. Look at Harden, Embiid, Draymond, D-Wade, etc. Even guys like CP3 and LeBron have looked a little heavy at times. Despite the extensive cardio that's involved, basketball players should not be confused for soccer, hockey, or tennis players when it comes to physical fitness. They're big people.
It was really only this season that it got so out of control with Luka that it became the central talking point. And that was due in no small part, I'm sure, to the league wanting to push a narrative that deflected from how shady the trade itself was. It has to be loving how much the public is eating this up (I'll see myself out).