Shot shell and choke design is more important than the number of pellets in a shell for getting pellets on target. A well designed 2 3/4 shell can often work better than a 3" shell. Better barrel and choke designs have also improved shot shell range.
The new loads such as "Heavy Shot" and Winchester's new "Blindside" are a huge improvement over early steel loads but are very expensive. Some of the new high velocity steel has also added a few yards to shot guns effective range. 50 to 60 yards is not uncommon for clean kills now with some new ammo designs but expensive to shoot. Learning good decoy set ups and calling the big birds in closer works well for me. I am horrible at long range crossing shots. At 60 yd crossing shots I seldom hit anything. At 35 yds or on jump shots I seldom miss. The new specialty ammo is deadly on water foul out past 50yds but not if I can't get my shots on target.