dynamic que problems

I need someone to explain to me in a shorter answer why i never get my primary in ranked with the new que almost every time i get my role i've won or at least done good as in three deaths or less and still got objectives but yet a majority of the games i get in i get my secondary is this a elo thing cuz if so i understand but its irritating me because i get in games and when it starts i can already tell i play better in that position than the person that is playing in it then. if im stupid please comment and correct me cuz as of right now i almost dont want to play ranked because i never get the role i want the most its like the old draft all over again. please some one tell me why!!!!!!!!