I’m no flex player by any means, but I’ll give something a go with one of my main characters is picked. I won’t do it great, but sometimes great isn’t required.
The attitude of locking what you want in is fine in QP, but when people bring it to comp and you see the last slot, which should be a healer or tank (depending on picked characters already) go to a Soldier/Tracer/McCree I couldn’t help but face palm. These people would rather have one their alt picks and throw the game. Pick what the team needs, you want the juicy SR right? So stop caring about your preference and start filling.