What is wrong with matchmaking?

Title, as above. I've been stuck with plat players in multiple games, and do note that I have never managed to grind my way past silver. I just have to ask what in the name of Teemo is the logic behind such asymmetry in the team composition when there are 4 golds and a plat against 4 silvers and a bronze? Yes, yes, I know that there "are few apparent skill differences" between the ranks until diamond and up according to the many elitists. I really fail to see the logic in matching players of different skill levels together, since it really does nothing and getting curb-stomped teaches nothing. If somebody knows the logic behind this, and would post it, I would love to hear.