Ranked Unfairness

This is straight bullshit. I've been playing this game coming close to two years now, and only just recently I've started playing ranked in the last 3 or so months. I was playing through some 3's tonight and I wasn't doing too bad, and then I hit my promotional series. My first promotional series game ever played. Tell me what the fuck this bullshit is.. My teams MMR was 1170 and the other team's MMR was 1566.. WHAT THE HELL. This is extremely unfair and super unbalanced. This is more of a complaint rather than discussion. Is there not way around this? Like, how in the fuck is this a fiar system for ranked? I've always had my doubts about the system but always came to the conclusion that it was a pretty balanced system, BUT NOT WHEN THIS SHIT HAPPENS.. Straight bullshit and unfair..