Ted Williams is very a good name drop onthe subject of hitting. And the idea of knocking in lots of runs a absolutely helps your team.
But no one really showed the flaw in RBIs than Joe Carter. His one year in San Diego, he batted .232/.290/.391 (.681 OPS) and drive in 115 runs.
He did hit .268 with RISP, which was a step over his awful average. But the big reason he had so many RBIs was he batted fourth most of the time that year and the 2 hitters in front of him were Roberto Alomar (.380 OBP) and Tony Gwynn (.415 OBP). Not everyone gets to hit behind two Hall of Famers.
In fact, most sluggers drive in themself more than any other individual teammate. With 24 home runs, Carter drive in himself as his third most frequent scorer on an RBI, behind Gwynn and Alomar. In fact he drove in Gwynn and Alomar a total of 62 times, which accounts for over 50% of his RBIs. Carter came up with 542 runners on base that year and drove in 16.7% of them, which is good, but not great. (Most middle order bats drive in 15-18% of the runners on base.). The average hitter that year came up with 429 men on base. Had Carter seen a league average amount of base runners, he would have had 96 RBI. Still a good season, but it drops him from 3rd to 9th in the NL that year...