Yep, that. I'm not going to play a new hero I'm inexperienced with (hello, Ana) in Competitive, until I feel I can play them well enough and have a good enough handle on their details. Same for existing heroes I just don't play enough, like Genji. I'm terrible with Genji. I'd pretty much never play him in Competitive, unless I was facing a team of Bastions pre-no-stacking-heroes (which never happened, but I digress).
So where do I get better at playing Ana, or Genji? Quickplay. Does this mean I'm gonna hose my team? No. If nobody's healing, I'll heal. If we need a tank, I'll tank. I'll fill the role we need. I'm not gonna play the third healer, or instalock Reaper every match. But I'm not gonna play Lucio just because you think Lucio is the best healer for this map; if you think Lucio's so necessary, YOU play him.
Not that I have any issue with Lucio. He's my most-played support for a reason.
Hell, I had a guy threaten to report me for playing Ana yesterday, in a Quickplay match. We were losing, he wanted to blame me. Maybe I wasn't doing very well (though I WAS playing as a healer, I don't play Ana to be an aggro sniper), but that's not reportable. And hell, I won the next two Quickplay matches with her.