The style of play was changing. The big serve and big hitting game was dead. It started with Lleyton Hewitt
Look at Murray, Djokovic, and Nadal. All play similar styles of each other, with different variations. Of that 3, only Djokovic to me is more versatile and can play in any era, thank God he tweaked his style of play so he could be able to last longer and not injure himself more
No one's doubting Nadal's clay court dominance. But no way he would win Wimbledon, US Open, or Australian Open in the 90s and early 2000s