There are so many players that have been just has good at 27-28 compared to 30-31. Kobe, James, Duncan, drik, nash, Malone, Jordan ect. I don't know where you got that got get worse at 28-29. But its not just that guys decline at a young age its that to many guys decline over all young or older. You see teams that have like 9 guys on there roster decline in 1 season. Also I have seen sever guys go down even at like 24-25 years of age. While yeah I don't want a guy that is 33 and say a 90 to still be a 90 or 89 by the time they are 37 but with the way things are right now you see just about ever player that is only 30-32 droping at least 2 points and a lot of them 6 points.
With the way it is right now you are going to see guys that are a 90 at age 30 go down to like an 80-77 by age 32 or maybe even worse. There should be more of a verity in players. Example would be Iverson went form being close to his prim to shell of his self in like 1 year where a guy like Kobe and Duncan didnt. Some players should have a slow decline and others should just drop off quik. They also lose points in things they shouldn't really lose points in like IQ. I had a sim where Kobe's IQ went down 1 and you see players jump shooting go down. Guys shouldn't get worse at shooting if any thing guys shooting should go up and things like speed and jumping should go down instead. That is why guys like kobe, Jordan, Malon, ect where able to play at all star levels has they got older has there athecisim went down they found ways to score in different ways and jump shooting was a big reason for it. look at Kobe even though he is way less athlectic then he used to be his jump shoot is way better then it was when he was say 21,22. Black griffen even though he is young and still in his prim his jump shooting has started to get better. So the first thing players should start to go down in is speed, jumping dunking not things like shooting and IQ.