Why do I get placed against plats in teambuilder?

Can riot do something about this please. I wanted to play some teambuilder before i hopped onto ranked and I noticed 2 members on my team where plat last year (I'm silver btw) so i went onto op.gg and found out I was playing with two golds, a plat player this year and a plat player last year. I looked at the enemy team and I realized i was going against a plat vayne that was diamond last season... How is this fair, i'm clearly out matched. (i was adc on my main) Listen before you start explaining how teambuilder works i know that it will match me with people more familiar with their champ so i don't play against a first time varus or something and wreck them but getting matched with a plat 3 vayne? who was diamond last year? how is that fair? I know teambuilder is trying to bring a challenge with some one with knowledge of their champ "equal" to my knowledge but this is a little much, to be fair though her team were silvers. It's not like this is a one time thing either, I've been seeing more and more plat players in my games but only when I go into teambuilder. I don't care if i'm good with the champion, i'm not as good as these people at the game itself.