Totally agree with Andy here, if you aren't very good or just plain don't understand a character then don't play competitive with it, learn it in quickplay. Let's say someone picks Ana, has a bad game and we lose but they clearly play Ana then I have no issue, we all have bad games. Let's say someone picks Sombra or Widow or any character, has an awful game, I check their profile and they have no comp time on them AND really low QP time on them, then I'd report them for griefing / trolling / bad teamwork pretty much every report I can find because they are ruining competitive games.
it doesn't matter what the character is, learn them in QP or custom games NOT competitive. I've had some amazing games with Torb mains, Widow mains, Junkrat mains, but they all had lots of time on them and clearly understood them, they didn't use competitive to learn new chars, that IS griefing.