This was definitely a thing just back in the 2000s. You had guys like melo, tmac, Paul pierce, wade, Dwight ect all decline in this age range or way before. People always mentioned lebron still being so good when he was 33. At first that seemed like an anomaly. Now, you have guys like curry, kd, kawhi, dame, lebron still(lol) jimmy butler, all still being in their prime at 33+. Is it an advancement in technology and medicine? Something else?
Seems more like your selection bias. Several of the current players you mentioned have had struggles with injuries in recent years, and you are ignoring some of the better players from the 2000s who did age gracefully.
Is it so hard to imagine a few years from now we will look back and see Kawhi’s last prime season was 2020 when he was 28?