the problem with Moira is also one of skill disparity.
Anyone with a bit of brain and attention to positioning (but not incredible amounts) can get to 3500-3700 with Moira. The problem is that Moira doesn’t teach you how to be a good support player. Who to save, when to run. Even Mercy, who doesn’t need to aim, can take more skill.
And if this 3500 Moira is forced for some reason to play Ana or Lucio, they play them at 2400 level. In a 3500 game. So imagine the disaster that that causes when your Ana is permanently in spawn.
Besides you can get 2 Moira 1 trick and go on a map where you NEED Ana (eg King’s Row).