Like you said, it will eventually. But this could be a Brady like trajectory. There are the reports that he spends $1M per year on his body. And certainly some injury luck involved too. But when you start at such a high peak, and you're fortunate to have smoothed the aging curve better than anyone else has in your sport, you can still be at 80-85% (or whatever it is) of what you once were. And whatever percentage of LeBron that is, it's still a very, very good player even at his age.
That being said it's super impressive that he hasn't had some huge dropoff. It's more of just little dropoffs here and there. He can't go all out all the time. He's not quite the defender he once was and doesn't get those chasedown blocks with regularity.