While I agree to a point, learn new heros and get good with them. Then just play them regardless of what your team thinks. It sucks because sometimes you get sad trolls who dont try, but there are more characters than Rein, Ana, Lucio, S76, Roadhog, and Genji.
Also, the more characters you know, the easier it is to counter the other team. If you do not know how to counter, you may never reach diamond, let alone master.
Thats my biggest Irk and why I cant play more than a round of competitive. People are so locked into whatever is trending with the "pro's" that they are unwilling to change it up and try something new or unexpected. If it fails switch it up again but at least try.
As sad as it is I find more people doing that in quick play than in competitive. Could be my rank is sub minimal as I never get through the placement rounds before I go back to QP lol. Not saying QP is great because its not but I find more "fun" to be had there right now.
While I am not great with some hero's I at least know enough of how they work to have ideas on countering or breaking up their composition.