Question About why Every Game is a Mindless Win or Crushing Defeat

So I'm aware of the MMR system but why is it even in place if it isn't being used? I'm bad. Not afraid to admit it. Don't play much, make bad calls, poor mechanics. Probably in the S4-B4 range skill-wise. So why do I get put into game with either gold players or pre-30 newbies? In nearly every game I play, we're either completely crushed with like half the enemy's cs and 2 items behind in every lane by 20 minutes or we're so fed we can just play like idiots and still win.

Deleted old account and uninstalled for like a year due to this trash in ranked and I see it still hasn't gotten better. Either you perform well on a trash team and lose, play like shit and get carried, or collectively stomp or get stomped. There's no competition. It's just not fun playing this game when there's no competition ever. Maybe 1/10 games isn't an obvious surrender by one team by 25 minutes.

How does Riot decide who you match with? Why am I playing with gold players when I'm not even level 30 OR good? Why do I get put on a team that steamrolls the enemy so bad that they early surrender or just int? Why do I get put on a team that gives the enemy jungler 7 kills in the first 15 minutes and never buys a single ward?

How about mixing some of the bad players on the enemy team in with the good players on my team or vice versa so it isn't a one-sided stomp? I'd gladly deal with longer queue times for a competitive, fun game!