Why high elo player and low elo player can still be a team?

GOD SAKE. WHY DEVELOPERS SUCH MORON ? WHAT IS THE LOGIC IN IT? I PLAYED 5 GAMES IN A ROW WITH UNBALANCED TEAM. 1 11XX PLAYER AND 1 25XX PLAYER IN SAME TEAM WHILE I HAVE 3 17XX PLAYER IN MY TEAM.FIX THIS ■■■■.