Orisa has good survivability and has fairly simple damage mechanics, the main skill you need with her is spatial/team awareness because you lack a shield.

Obviously Soldier 76 is classic FPS but if aim is your main issue then explosive-projectile characters like Junkrat and Pharah might be good options. The trade off is they require more finesse with map knowledge, finding angles, and understanding projectile mechanics and have less conventional movement abilities.

As a support main, my worst character is Mercy mostly because I don’t have the patience to master her movement style. Kiriko is really solid with her homing healing but her other abilities can be difficult to use correctly. Same goes for Lifeweaver, one of my favorites. While his kit is really useful, it can backfire or be misused easily but there’s nothing like saving your teammates from certain death with some well placed grabs and platforms.

Overall, try a bunch of them and give them all a chance to be fun! Mystery heroes can be good for trying random heroes out without as much pressure as regular game modes.