The true PRIME age starting point for most players is around 27 years old. Because players come in the league so early now. You may be able to move that to 25.
It's basically when your muscles are at their peak and your entire body is at peak performance. it's also when you're grown enough to sacrifice more things to get better like No BS foods and instead you eat right. You also work out properly, stretch like you're supposed to, and listen to your trainers. you now have a regimen that is fine tuned So you get more bang for your buck their also.
Another thing you do as you get to that 27 age or so is that you have played in the league and played basketball long enough to know pretty much everyone's tendencies (your teammates, your opponents, the coaches all all sides and if you see a new player you can guess more accurately based on how they play what their tendencies will be. basically you've been there..done that.
Lastly. The closer you get to your 30's you stop caring what other people think. This makes you a better player because you're not longer as indecisive as you once were. you make quick decisions and are willing to live with the consequences of those decisions.
IF 2k did the formulas right. Then you should push that peak age up to around 25 or so. so it gives your guys enough time to reach their potential. now you also must realize if 2k made it realistic its going to be some what random but their is math to it as well. How many guys come in with crazy potential only to either fiz out early in their careers due to them not being ready to work that hard? or just happy to be in the nba, or not liking the pressure of being that good on that big of a stage? How many guys end up solid role players or borderline stars but not quite where they should've been. This is most of the nba to be honest. The rest is a very small percentage of players who truly reach and max out their potential. it doesnt mean you're going to be a start. it means you are as good as you are ever going to get. if thats in the formulas. then i could see a scenario where your guy shows 91 potentional in year 1 and by year 4, its 75. because ole boy just aint about that greatness life.