Dynamic Queue

I am a Platinum V player and I have been in the plat elo for over 100 games. I just played a solo queue match where i queue'd into a 3-man premade on my team. The match was found in less than 3 minutes so i figured the system found my skill leveled players for both teams. As i get into game, I saw unbelievable mistakes out of my friendly MF who would insta cancel her ult and sit in the middle of her team, but i felt she was just a "weak link" of her premade group. After the game, which we won thanks to a fed Yi, i checked my teams rankings. 1 was Silver IV, 1 Silver II, 1 Silver III, and a player in his PLACEMENT matches against a team of 5 gold or higher players. Why does this rank system even exist if the skill difference is further than a normal blind pick? I cant queue with a friend who is over 1 tier away from me but i queue into a team where everyone is MORE than 1 tier away? If Riot cant get it right in neither low elos nor high elos, what exactly is ranked GOOD at? This has happened in a few of my games already and I know many think it's about by MMR but I have stayed in plat IV or V since February. Is anyone else having this type of experience? I am a huge competitor and really miss matches with evenly skilled players on both sides.