Okay, Okay, Nice...

Most likely because there wasn't enough people for your match, and therefore riot put in a season 6 gold/plat player.

Playing Yasuo in ranked I see [zombie-brand-mindblown]

Looks like it's just karma for playing Yasuo to me. Also it was flex, which is known to have balls matchmaking. And there was an unranked on enemy team too, so pretty even really.

If you think playing with a bronze on your team is bad, try playing against a Master.

aw come on my yasuo stats arent even that bad :D