Fixed matchmaking for the dynamic queue my ass

Normal game matchmaking always was broken ,and always gonna be.Start to play rankeds.

It's because the other people with you have a high MMR. The only difference between ranked and unranked is that in ranked you can see an idea of how high you are in MMR via tier and division. They both use the same matchmaking criteria. And it works just like the StarCraft 2 matchmaking.

That plat was partied with someone with a lower MMR so matchmaking tried to find a general medium between the two extremes. So each and every player in that game was of an ELO rating between them. Someone on your team had an MMR similar to the plat player, even if they were unranked (cause they may have played 2000 games and won a high %of then for example) or it could have been you because winning a lot of games in a row as a gold-level MMR will put you against platinums.

Edit: remember that a while ago when Riot said that if you constantly win against people in a higher tier then you will jump a whole tier instead of a single division.

Every time you win a game your MMR goes up, and the more you win in a row the higher it will get temporarily boosted until you start facing people at a higher tier. And that's where their changes come in, cause if you keep beating people of the higher tier, then come promos expect a big promotion. If you don't win against higher tier, then your ELO will be readjusted back down slowly.

Log out for a day and it'll normalize again with proper adjustments.
EXAMPLE: Duo queued with a friend when I got into gold. After 5+ wins in a row, we had a game where we were the only 2 gold(5)s, all others were plat. We got face rolled and called it a day. Next time we were back to facing high silvers and low golds.