Ranked Matchmaking

I feel like I’m hard stuck diamond 4 because I get paired up with horrible teammates who are new to the game. 
Like JUST NOW I was paired up with a Bronze level 32 and a Gold level 72. I’m a level 275+.

The teammates push when they shouldn’t, run off on their own and leave me to 1v3, and then throw the game because I ask them to help me. 
I’m not a bad player either. My average is 1200 damage per arena match and lately all I’ve been dropping is 4ks and almost 5ks because they don’t help me. 
So, why the hell am I still being paired with these horrible players instead of at least giving me a platinum teammate? Because I go against diamond and masters and level 500s but you wanna give me people who are BRAND NEW?!!

Makes zero since. Might honestly quit if it isn’t changed.