The two teams will on average be approximately the same mmr, so occasionally relatively low rank players will actually be the aforementioned gods how have mmrs well beyond their rank, and that's why they're in the same game. Duos occasionally also throw a wrench into the mix. It is very unlikely that your mmr is specifically somehow broken, or that matchmaking on the whole isn't working as intended.
Still, if both teams start looking mid-low silver on average (excluding yourself), then it's probably fair to be worried. One off games here and there with some weird rank mismatches can be attributed to a variety of things, including how mmr and rank don't always match for people (so getting matched with someone a lower rank than you could mean that your mmr is low, but it could also mean that their mmr is high, hence you gotta look at the big picture and ideally over multiple games).