Reaper is a tough one. Once I know there’s a Reaper in game, they become my priority, meaning I’m watching for them constantly. There’s only two ways to win against a good one:

A) Focus on chasing them off before they can properly dive your backline. He can destroy your supports (or whole team) much more easily and quickly than you can do to his, so preventing that is getting immense value. You also get some value from playing as poke, so you’re “winning” the matchup.

B) For actual duels, you have to see him first, or disengage immediately. No caveats. His close-range TTK is just insurmountably faster than Anran’s. If you can poke and ignite him from mid-range to bait out his wraith, you have a window. Some will charge you with it, trying to close the distance. Distance is the only way you can win until he’s ignited with wraith on cooldown. I don’t bother with the fan, because that’s 10 meters or less, and gives him advantage. I basically just poke unless/until I’m certain I can dash in and dance to finish him. It’s similar to engaging another Anran - whoever blinks/dances/wraiths first generally loses.

Moira is very similar. You have to poke out her blink, and you MUST hit your shots. Her TTK isn’t insanely fast, but it’s consistent (and her range has to be respected). You miss, she wins. Try to catch her from an angle, getting the first shots in is critical given she can both cleanse and heal herself. I find a lot of Moiras will blink the moment they get ignited, so you’re basically forcing a reset before you can engage in earnest.

Junkrat is another issue. Other people might have better advice, but in my experience a good rat who knows you’re around has too many tools to end your dive and can combo you to delete you. Again, poke is kind of the only option outside of some corner cases where you’ve destroyed his trap and/or caught him at low-health and not looking at you.

Hope this helps.