I think giving credit to Rondo for Pierce's success is a bit far fetched, but KG certainly benefited (offensively) by playing with Rondo.
Pierce and Rondo had a complicated on-the-court relationship. Paul always wanted the ball in his hands more but was always a more efficient scorer when he didn't control the ball as much because the defense couldn't load up against him so easily. The two most efficient scoring seasons of his career (by a decent margin) came during seasons where Rondo was controlling the ball much more than him.
By the same token, they came in years in which you had players like Ray Allen and Kevin Garnett drawing a lot of attention themselves (to go along with Rondo of course)... so I just don't buy the notion that playing alongside Rondo somehow extended their usefulness or something along those lines.
If that's the case you'd expect his best year to be 2008, when those guys were younger and better and KG and Ray commanded more attention than they did a few years later. Or maybe 2009, before KG's knee injury. That's not the case.
A point of fact, Pierce had his most efficient months last season when Rondo was out. Many things contributed towards it certainly, particularly chemistry with the rest of the roster finally coming together, but there's that.
Point in fact, PP had a knee injury that had a noticeable effect on his play, especially in Dec and Jan. Danny talked about it during one of the games. That had a bigger effect on Paul's play than anything else last year.
No that doesn't mean one thing or another, and drawing up conclusions in the manner you're doing considering that countless variables that go into why a player is scoring effectively is not that much productive.
Paul Pierce has and has always been a very capable shot maker and shot creator, mostly with the ball in his hands. Does playing with Rondo help? Sure, but not to the extent that people want to imply.
Pierce has always been a very capable shot maker and shot creator. That I agree with. However, it seems fairly obvious that he'd have an easier time scoring when someone draws the defense away from him and passes him the ball than he would when he's trying to create a shot against a defense that's focused on him. That you seem to disagree with.
Where have I disagreed with it? The only thing I've really contested is the notion that due to Rondo, Pierce's effectiveness in this league has been prolonged, and I have also contested the fact that Pierce had some of his most efficient shooting in recent years is sign that Rondo was the cause of it.
It's ignoring a lot of factors that have influence the result, including improved 3-point shooting (heck, he was 3-point All Star champion), and playing with 2 other future hall of famers, which limited the amount of double teams he encountered. And on that regard, when he got double teamed, it came from Rondo's defender more often than not to take that into consideration.
So yes, overall Rondo had a positive impact on Pierce, but not to the extent of:
"I've long thought that the success those guys have enjoyed well into their thirties was largely due to having an elite distributor like Rajon Rondo around to make life easier for them."
At least as it applies to Pierce and his offensive prowess.
By the same token, I'm sure plenty of Rondo's success has come from playing with a guy like Pierce and KG, but I also acknowledge that Pierce in particular has hindered Rondo's development some, at least as far as production in the court goes.