Look, when it comes to top-notch, back-to-the-basket offensive threats, we're left with two of them in the league - Tim Duncan and Shaquille O'Neal. Any guard (that isn't named Kobe Bryant) can tell you that a back-to-the-basket post threat makes the game a lot, lot easier. Not only does such a player create foul trouble, but he has the ability to see the outside players, making it easier for him to pass to them when they're open...meaning they'll get better looks. In addition, that means eye contact is quickly and easily available.
Any face-up player is going to have an advantage playing with Shaq, no matter how old and washed-up he's reputed to be. Add to the fact that O'Neal has good footwork, and a great passing eye, and it's going to be hard for his basketball skills to decline appreciably just because of a few steps backward on the physical skills.
Sure, Shaq's slowing down. But so far, only Detroit has shown any real signs of understanding how to exploit that.
The only place on the basketball court where Shaq is truly ineffective is on the sideline. And I don't see that changing.