System has nothing to do with it, he was already washed up when he went to Madrid. Also, why do you diminish his achievements by saying he played in a good team? Most Ballon d'Or and top players in general do anyways.
I absolutely dont want to diminish Kaka, cause he was a fantastic player. He wasent washed up imo, cause in that last season, he was goddamn impressive.
But i somewhat see the messi syndrome in him. When surrounded by the right players that carry the team, he can trive and bring the team 4 levels higher. when placed in a difffrent team, it becomes obvious he isnt a carrier, and will do significantly less.
milan was carried by many players. they had an insane defence. midfield carrier by pirlo/gattuso/seedorf, and up front was a shevshenko that was arguably the best striker in the world at that point. It was ideal for him
And he totally deserved that ballon d'or.