GRMember

Tanks aren't supposed to take out flyers in overwatch, but they are supposed to help by keeping pressure on them and using abilities when they can hit them at closer ranges, like rams vortex or orisas spear. If the flyers are playing angles super hard and using cover, mauga is a great pick unlike you said, if you only shoot one gun at a time you can mow the flyers at range and get extra tick damage from the fire gun for when they use cover making them have to wait longer to be in the fight again. Not saying tanks dealing with flyers isn't expected in rivals, but overwatch doesn't completely expect tanks to deal with flyers, they are expected to help where they can, and worst case tank can swap to mauga and ensure they are suppressed long enough to gain space.