I'd quit. Free hero choice is probably the best thing about overwatch. I don't wanna be forced into roles that I don't feel like playing at the given time. Plus, OW is unique in the aspect that viable comps are independent of roles. You can go quad tank, triple dps, triple support, builder comp, triple tank, pirate ship, double sniper, defense only etc. And there's a chance to win the game even with the most unique comps if you can make more synergy with them.
Edit: also, it's not like the current system hinders your climbing in any way. Performance based SR still exists below diamond that you will end up where you belong regardless of comp. And above diamond, I guess the game expects you to make workable comps based on your own sense and skill. It's upto the community to compromise rather than the game forcing it. And even with that it's not like you lose the minute you have a bad comp. I lost to 5 DPS, 1 healer yesterday. Even with our 3-1-2 comp, they beat us mostly cause their snipers wouldn't miss shots lol.