Unranked keeps fighting higher ranked (Silver 2 - Plat 4) opponents

Why does this happen so much I cant have fun when there is a Plat Zed and Gold Draven on the opponent's team. Half the time they have abandoned their lanes at 15ish minutes in and are now just roaming for kills and ignoring objectives until they have 20 stacks on sword of the occult then just force mid. I'm not the greatest player and have never touched ranked so why am I fighting these people in normal blind pick? Also not sure if right category this is my first post.