What's up with match maker in team builder?

I'm only Plat 5, and every single game in team builder solo queue I get matched up against at least one diamond or master league player. And we usually just get absolutely stomped.

When I check on op.gg, the enemy team ELO is on average around 30% higher than my team - a huge amount. In none of my games is my team's ELO higher than the opponents.

Is anyone else experiencing this imbalance?