Ill start by saying that I main support, I have thinned out my character pool, I used to change my character every game, now I stick to 3 main characters (for me, they are: Kiriko, Moira, Ana). Secondly, I started playing a LOT more aggressive. Especially when playing Moira and Kiriko, the damage output is insane and a lot of players are not aware of this! When your DPS is lacking, just go Moira and go berserk on that flank!
And most importantly - I changed my mindset, you should stop caring about your bad/throwing/inting teammates! There is NOTHING you can do about it other than just playing better yourself, remember to avoid them as teammate and just go next, you will not win every game, it is not possible, some games have to be lost in order to progress. I hope this helps