Ever since hero stacking (when there's more than one of the same hero on the same team) was removed from Quick Play, that mode has become a nightmare. I was not able to play the heroes that I was most comfortable with because someone else had picked them, so I was forced to choose someone else that I didn't know how to play, just to fill a role. If my team was missing a tank, I was forced to pick a tank hero to balance the team -- even though I didn't know how to play one. This would lead to deaths, losses, and frustration.
Players shouldn't be forced to adapt to a whole new character just because of one game mechanic -- just let them play their own heroes instead of forcing them to use someone they don't have experience with. I imagine a lot of readers are thinking that you should just practice and learn new heroes, but I disagree. Practicing a lot doesn't necessarily mean that you'll magically become good with a character. Certain gameplay styles may just not mesh well with your set of skills as a player -- which means certain heroes will always confound you.
I can see why hero stacking was taken out of Competitive for better balancing, but I don't understand the decision to remove it from Quick Play. Quick Play should have been given the same treatment as Arcade, since Quick Play is not the same as Competitive. Plus, hero stacking can prove to be fun in public games that aren't competitive. What's the harm in that, seriously? You can switch characters, after all. So if you see an army of Torbjorns and his turrets, pick a hero who counters that.