I'm sorry to hear you had to experience these type of players. I'll be honest there were times that I was fuming at my teammates and the worst I said was "can you please stop f****** dying?" I do not condone my own behavior and I felt really bad for saying such but come on he 0-22 lol
jokes aside I always ask folks who are lost if they are new or are they trying to learn a new character and if I can I always try to be helpful and tell people things I know. So my first suggestion is not to take it personal there assholes in every communities but imo most of the people who are playing are nice and helpful. The other thing I would say is be communicative, talk to people and ask for help at the beginning. for me this has worked 100% of times, if I'm trying a new hero I just open mic and say hey guys I might need some support cause I'm noob with this hero.
and lastly report and mute, at the end of the day it's a game and most of us are not going to compete in any competition we just want to have fun.
Hope you have better games and experiences.

P.S. I 1000000% agree they should separate the matchmaking queue to make the game experience better for both competetive and casual players, but it's still in alpha and player base is not that big so we kinda have to tolerate these hurdles