I dont understand how the ranked system works

Atm i am silver. I'm playinga bit of ranked flex for fun with 4 friends and we meet a full premade team aswell. We have 3 ppl in silver 2, one in gold 5 and one in gold 3. We meet a team of 1 plat 3, 1 plat 5, and 3 in gold. How is that a fair matchup? Is this because we have a higher MMR? Whats the point of MMR then? MMR should just be your ELO. If we fight against people from plat and gold we should BE plat and gold. How are we supposed to reach out goal of high gold when we fight people from plat in silver already?
Report as:
Offensive Spam Harassment Incorrect Board