I keep getting paired up against plats in norms, and now it's gone up to diamond players

First of all I suck and am only a silver player. I'm not good at league so I play it just for fun mostly on normal. But it's been happening where I go up against plats players lately and diamond players recently where I have little to no chance of winning. I'm also getting pair up against high rank premade players almost every game. I know ranks doesn't say everything about a player but it does say something when I'm getting my butt owned most of the time from the high ranks. I get completely destroy along with my team that I get pair up with and we just have to surrender at 20. I do not find it fun and enjoyable at all. The match that I play with high rank players doesn't feel like a near 50/50 chance of winning where mistakes or good setup can change and give you the chance to win the game, more closer to 30/70 or even 10/90. If anything, I want to know why that the matchmaking system is the way it is. If it's somewhere explained on the forum or somewhere else, someone please give me a link so I can go check it out. Thanks!