And how can Torb/Symm/Hanzo/Widow mains manage to stay at GM level? Everyone knows who they are and what they will play (if they don't they can just hover over their profile before the match begins and see what they play), yet they stay there with pretty decent winrates.
I can't believe how hard it is to accept that people can be skillful enough to be able to play against their counters in an environment where opponents will rarely have the level of coordination and communication required to deal with unusual picks played well. This is not the pro scene, the six members of your team didn't split beforehand the roles so that they'll be able to counter all situations. They might not have a Pharah player for your Reaper, or your McCree might be better than their Pharah player.
Just chill and let everyone play what they know best. You might be surprised by the amount of games you end up winning with "suboptimal" comps.
Stop playing comp if you think this way and play QP