Looking at the cup winners of the past: a good, consistent, highly touted goalie was nearly always present. Vassy in TBL. Bob last year (wasnt picked by FLA, but was pretty consistently good). Furthermore, many of the winners were home grown like Murray in Pit, Bennington in STL, Crawford in Chicago, or Holtby in WAS, or Quick in LA.
Obviously, there are also many counter ones: Hill and Kuemper stand out accordingly.
Nevertheless, it seems like having a solid young goalie is of great value, even though you can win with a journeyman or a mediocre goalie. However, I would bet there are countless teams that had SC winning rosters, but were sunk by horrific goaltending.