The fact that he was a very good pitcher only adds to his legend. But consider the following:

1. The dimensions of Yankee Stadium when it opened in 1923 were officially 296 down the line & 350 to right center (but were rumored to be significantly shorter).
2. The talent Ruth faced should basically be viewed the same as we view Bill Russell's NBA competition in the 1950s & '60s. No black players, little to no latin players, and no Japanese or Korean players. So his competition was limited to just the white players when the country was 1/3rd of its current population.
3. The average fastball Ruth faced is estimated in the low 80s, with baseball's power pitchers like Bob Feller topping out at 90 MPH. Additionally, he rarely had to face left handed specialists as starting pitchers were expected to throw 9 innings.

Now I don't discount Ruth's talent, just like I don't discount Bill Russell's. Great players would adjust and succeed in any era. And modern training, equipment, nutrition, etc. gives today's athletes any advantage. But to discount one player because of a factor while not looking at factors impacting success for others is intellectually dishonest.