Unfortunately a support is usually only as good as the team they have. Playing Mercy effectively on a bad team is nigh impossible from how poor they can be at defending you or taking advantage of power boosts. Most of the time your only option is to play Lucio since he's got the best survivability of the supports.
90% of the matches we lack damage output and a healer, so yeah I go Lucio.
There's only so much I can do and I would rather lose playing the team game than lose trying to be the MVP, so I feel like picking support is in the cards for me.
The times I play Mercy all I hear is "I need healing" as they run away from the point or away from me, and then I die with ult up and they die after I do.
Also how many times do I need to call out someone before people typically react to it? I try to watch every entrance and call things out but it's a miracle if people react to it.
I was hoping competitive would be a little less YOLO than quick play, and I know it's probably dunning-Kruger effect at work but I always feel like the other team is a well oiled machine and we're a car with square wheels.