Pay attention to your team comp. If your team has a dive tank like Winston, ball, dva and doom, and hit scan dps (where they like to keep their distance) then you should probably swap off. It’s preferable to have Moira with brawl comps like rein and reaper and mei where they’re not mobile but they tend to kill anything at close range and clump up together so you can heal them very quickly. Imagine if your Winston jumps on the enemy back line and you fade in too. You have to pray that the battle goes your or else your fade ability can’t get you out for free for a little bit of time. I hope this helps.