Can you really tell the difference between Steve Nash and a 32 year old? Can you tell any difference between a 32/33 year old Pau Gasol and a 27 year old? Camby is still in this league. Look at Grant Hill and Jason Kidd. Something has changed.
In regards to this part, yes I can tell the difference between a 27 year old Nash and a 32 year old Nash, but I don't really think anything has changed.
In the 2000's, you had Kevin Willis, Dikembe Mutombo, Cliff Robinson, Karl Malone, John Stockton, Charles Oakley and Michael Jordan play past 40.
In the 1990's you had Herb Williams, Rick Mahorn, Danny Schayes, Charles Jones, Robert Parish, John Long, and James Edwards play past 40.
And only a very few players (Kareem, Cousy, Nat Hickey) in all the years before the 90’s.
So in the 2000's you had 7 guys play past 40, but in the 1990's with less teams you still had 7 guys play past 40. And so far in 2010's we've had 2 guys play past 40 (Kurt Thomas and Grant Hill). So to me it doesn’t look like anything has changed here except the NBA added a lot more teams starting in the late 80’s. Unless you think James Edwards, Herb Williams, and John Long were the early adapters of HGH.
And a lot of these older guys just get by on name recognition. I think there's a big difference between Steve Nash and Jason Kidd now and 5 years ago. Jason Kidd only averaged 6.2ppg and 5.5apg last year on 36% shooting. I think everyone of us can see a huge difference between Garnett, Pierce, and Ray Allen now and 5 years ago.
And let's not forget rule changes that encourage must less contact. Players now don't go through the beatings that players from the past had to.
Not to say there isn't PED use, but player longevity isn't an indicator.