What do you know about Ruth's defense? Honestly?
And seriously, you need to come up with a new definition of the phrase "isn't that great."
Ruth led the league in OPS 13 times. Aaron did it 3 times. Aaron's best OPS+ was 194 in 1971. Ruth topped that 11 times. And in 9 of those 11 seasons, he played more games than Aaron did in 1971, in spite of the fact that the schedule was 8 games shorter. In fact, Ruth's career OPS+ of 206 is substantially better than Aaron's best season.
So explain to me what you mean by "isn't that great." It's definitely not the same thing I assume people mean when they say that. You realize great means large, not small, right?