You should try to win in QP games, but you're not gonna go full sweat in it every time. Especially if you're trying to learn a new hero. Team comp isn't really relevant in QP. Sure, try to win, but don't stress it so much. Everyone has their reasons for playing in QP, and not one of those reasons is to win every single game. Do most people want to win? Definitely. But they're more focused on whatever their individual reason for queuing casual is.