Ranking System

Is MMR really a good enough way of determining who should play with who? Just had a Bronze 2 player (lissandra) in my game and while his/her mmr was supposed to be silver 5 (im s3, i know im not good at the game or anything like that) and they just didnt know what to do. The enemy mid laner (ahri) came bot 24/7, which is fine i even killed her once or twice, but my laner didnt understand the concept of pushing the wave to make ahri miss cs or just to get tower first. you know, punish the laner for leaving lane, since liss couldnt move fast enough to counter gank. What goes into determining MMR besides win rate?

As a side note, idgaf if I get reported, I will flame the hell outta someone like this and will always flame someone that feeds. This, imo, might be because of who i am as a person but also i think bc i play adc. Generally i will do decent in lane, hold my own or win, but then since adcs take so long to ramp up a fed mid laner easily shits on me in team fights. so at the end of the game my kda looks like trash and i get flamed every time for being trash and even if i stand back in team fights i get accused of not being in the fight. So honestly, fuk this liss and anyone that plays like her. Imma flame the heck outta anyone and everyone to my hearts content from now on.