RBIs are largely a product of the team. While they are not useless, there are so many better ways to assess a hitter.
Mookie has more RBIs than Hanley, but Mookie also has had more runners on base than Hanley (306 to 299), and more plate appearances (563 to 443). Counting the batter himself as an RBI opportunity, that is 869 chances as opposed to 742 chances.
That's not the best way to look at things either, but I think that shows why just looking at sheer RBI numbers is not very telling.
FTR, Mookie has batted in 18.954% of other batters, while Hanley has batted in 10.033% of other batters. Mookie has obviously been better at getting other batters in.