KG is definitely still top ten. I think your valuing stats a bit too much to realize what KG does. We should all know by now that KG would rather pass before shoot, and get other players going. He's more of a go with the flow type player on offense, a player who has no problem deferring. I know this is really cliche, but Garnett is one of those guys that makes the other guys around him better. He allows other players to do what they do If it's going to help win the game.
When player's around him are doing there jobs Garnett isn't going to look as impressive. He'll put his team mates in every position to succeed possible. It's when his teammates don't pull there weight that's when the stats show you how much of a top tier player he is. When players aren't pulling there weight he tries to do it himself (and does a fairly good job) so the scoring, rebounding, and assists numbers jump up. That's when you start to see how dominant he really is when he helps otherwise horrible teams over achieve. It's the same thing that Lebron is doing now.
As long as KG is on a team like the current Celtics. A team with 2 other all-stars, and with guys he trusts to make plays he's not going to look as impressive as he really is. On a team like this one he's just going to fill his role to the best of his abilities and try to help his team get a win. If we needed him to put up 20/12/5 I'm sure he could, but we don't we just need him to play defense, rebound, and create shots for others.
As for him not being clutch, I agree. He becomes a bit more out of control with the ball in his hand, and makes more mistakes when it's crunch time. In my opinion, it's a personality thing he's to intense for his own good at times, it's like he can't calm down, but that's why we have Pierce. Garnett is the guy who doesn't want the pressure of taking the last shot, and Pierce is the guy who loves the pressure, it's the perfect marriage.