Your intelligence and technical ability goes as far as your ability to match the pace of the game.
Toward the later years Iniesta lost his stamina and speed. Becoming more tired leads to poor decisions, poor touches, etc. Xavi lost his mobility after 2012. Much like Puyol, they felt they couldn't benefit the team anymore so they stood down. Ramos is still as fast, mobile, and strong as he was 10 years ago. He doesn't miss a game unless he's been sent off. He's a machine.