What actually goes into matchmaking?

I'm actually curious as of lately; I feel like matchmaking has become more or less flipping a coin when queuing to see who you get as teammates.

Does anyone actually find consistently balanced teams? or does it happen roughly once every 3-4 games? It just feels like your either dominating the other team or being dominated (Goes both ways).

I've gone on 11 game winning streaks from just getting better teammates alone; with barely little to no effort from me at all. Where my skill has 0 equation into actually winning. Just the matchmaking rewarding me ect while punishing the other team. I've also gone on massive losing streaks even when getting S ranked and making plays/warding etc due to multiple team-mates going 0-12 etc.

I've started looking up statistics after matches and noticed a lot of times - one team is completely one sided. You'll have one side with much better statistics over their last twenty games.

Is there any room for improvement? A person who wants to see more consistent games that revolve around skill and not luck.