I've made the Westbrook/Rondo argument many times before, but some CliffsNotes:
-OKC needs Westbrook, or a scorer like Westbrook, in order to keep teams from smothering Durant. We saw it in the playoffs last year, and someone made it a point in this thread earlier, I believe: You put Rondo on that team, and there's no reason they're not going to rotate all of their best defenders onto KD, who will be forced to play all 48 minutes of every game because they're not scoring enough points without Westbrook.
-Rondo is great at many things, but his strengths don't lie on being a threat to score on every single possession. That's exactly what OKC's offense demands -- a pair of wings that demand absolute attention on every possession from 25 feet in. The fact that OKC's offense is still super basic is partially to blame here, but the idea that Rondo will make guys like Perkins, Butler and Ibaka better by getting them the ball is dumb. They're not great offensive players, they're never going to be great offensive players (Butler's good, but he's real old).
I'm not sure which young players you're referring to that aren't being made better by Westbrook so much as they're not seeing the floor because the Thunder are trying to win a championship, so Scott Brookes is playing the players he knows are, you know, already good at basketball.