Can someone explain the Matchmaking-System for normal games for me?

Hi Summoners, I'm Overloadroad and I'm just playing normals. I started noticing this thing half a year ago, and nothing changed. I'm currently Silver 5 (I only played 14 ranked games), and in 8/10 normal games that I'm being matched with, the enemies are higher tiers (gold and sometimes even diamond) than me. What's even worse, that the players of my team are just silvers, bronze or unranked. Take a look at my last game as Middlesticks:

http://matchhistory.euw.leagueoflegends.com/de/#match-details/EUW1/2739974577/221140296?tab=overview

As you can see the lux was unranked, and I had no problem dealing with her. But Riven and Kha are Gold, and Ezreal was even plat last season. This would've been fine, if my team had similar rankeds. But would you look at that: Morgana lvl 21, Vayne Bronze, I'm SIlver 5. Is this supposed to be like this, and if so, why? Some of you may say "You can learn much from playing against higher divisions players". No. You can't learn anything from being stomped to death for 20 mins. I know it's just a normal game, but I'm a player who ONLY plays normal. It's even worse for the morgana player, she's still new, but this is really bad for her (and for new players in general) I really want to know if it's just for normal games, and if there are any other players who have the same problem.