Overwatch players want Pharah nerfs following the nerf of hitscan characters such as McCree, Soldier, Baptiste, and Ashe. The changes to these hitscan characters will still allow for optimal damage output when within their effective ranges, but they will see a decrease of damage output scaled at 30 percent of the maximum falloff range as opposed to the previous 50 percent, according to Blizzard patch notes.
Since Pharah is able to deal damage and sustain herself at long distances, these changes will significantly impact the amount of damage hitscan heroes can dish out in an attempt to counter her. Since heroes such as McCree, Ashe, and Soldier are go-to picks when effectively dealing with Pharah, nerfing their fall-off damage without also nerfing Pharah will lead to an imbalance favoring the airborne hero.
According to a Reddit post, these changes impact hitscan heroes even further when considering a Pharah with a Mercy pocket. With a critical rate of 0.5 to 1.0 hitscan heroes take double to triple the amount of time to kill a Pharah with a Mercy pocket when at a 45+ meter range than before the nerf.
The difference between killing a Pharah in 15 seconds compared to the previous 4 seconds is significant, which is the primary reason Overwatch players are calling for Pharah nerfs.
These changes directly impact Pharah's survivability and her advantage in the air at great distances.