The truth is that GMs win divisions and managers win WS. You can load a roster in a way that it has a great chance to win a division but how you utilize it will determine where it is in October
I think what so many people don't get is you really only need TWO really good starting pitchers - and as long as you have decent middle relief and a lights out closer, you can go far in the postseason as long as you have a way to produce runs.
The greatest single season STARTING pitching staff in baseball history (per the numbers etc) was the 1997 Atlanta Braves team. And we can only blame Eric Gregg for one of those losses.
Bill James is generally regarded as the MLB stats guru and to his credit, he changes his mind on issues when more data or a better interpretation of the data is available. This is a dated reference, but here's how James ranks the pitching staffs as in "best of the decade":
1906 Chicago Cubs - lost WS
1913 NY Giants - lost WS
1926 Philadelphia Athletics - (finished six games out and in third place)
1931 Philadelphia Athletics - lost WS
1942-1946 St Louis Cardinals - won 3 WS but definite outlier influenced by WW2
1954 Cleveland Indians - swept in WS
1966 Los Angeles Dodgers - Koufax/Drysdale swept in WS
1971 Baltimore Orioles - lost WS
1985 Kansas City Royals - won WS
1993-99 Atlanta Braves - highest in 1997, won one WS
All you need is one guy to come up huge and do most of the legwork (Lew Burdette in 1957, Mickey Lolich in 1968, Curt Schilling (with heavy support from Big Unit) in 2001, Madison Baumgarner in 2014), you don't need a lineup of HOF pitchers.
Look at who beat the Braves, ending the season in the prime years:
1991 - Jack Morris and names from a phone book who pitched okay
1992 - David Cone and Juan Guzman (Braves won both Morris starts btw) plus a great pen
1993 - Curt Schilling and middle relief pitching over their heads plus a solid Danny Jackson start
1996 - what killed the Braves was NY's middle relief corps in games 3-4 and mistakes
1997 - Kevin Brown and Livan Hernandez with an Eric Gregg assist
1998 - Sterling Hitchcock and a superior pen
1999 - Clemens, Cone, and a lights out bullpen
Not one of those teams had a superior STARTING staff to the Braves, none of them even broke even.
But once you got past the first six innings, the Braves faced a series of teams that had better pitchers BEHIND the starter and could keep the game from getting out of hand.
Atlanta didn't beat Cleveland in 1995 because of the starting staff alone; they did it because Borbon Jr, McMichael, Pena, and Wohlers did their jobs for the most part.