Seems to be a trend but players that have an explosive element to their game tend to decline quicker. Look at Scholes vs Gerrard or Terry vs Ferdinand. It’s why I think Kane will be the same quality till he is 36-38 as he has never had any explosive element to his game unlike Son who does. It’s almost the advantage of being slow, you learn a different way of playing and go on longer.
Kane was deceptively quick in his earlier years (and actually had a burst in his locker), but saw the writing on the wall in his mid-20s (when he kept on getting injured) and evolved accordingly.