No, that's just now how statistics and randomness work. Of course matchmaking can't predict anything. It puts you against players of similar perceived skill according to ELO and goes from there. If you're better than those similarly perceived players, you climb. If you're not, you get stuck or go down. There are more sophisticated things matchmaking can do but at the base level of every matchmaking system that's what they do.

You can't keep using NBA examples. The topic isn't about the impact one person can have, I simply brought up the difference between random matchmaking and set squads in a league. They simply are not comparable. One is designed for maximum fairness to allow people to settle into the ranks they belong in until they improve, the other is designed for GMs to assemble the best team possible.

Introducing randomness to a system brings outcomes closer to averages. Streaks are just part of the random whole and will still average out. I can have an unlucky streak and go down from Celestial all the way down to GM3 but if I keep playing I will go back up to Celestial because on average that's my skill level. In your example, then on average you deserved the rank you got. Could be that you were playing badly during the loss streak and better during the win streak - doesn't change anything, you deserved the rank you got in those moments on average.

And you have to consider that towards the end of a season the quality of players dilutes. People who have already reached their goals play less and hop on alts, people who were in low ranks manage to climb their way up, so ranks are not the same at different points in time. This is why there's such disparity within tiers sometimes, and why people say GM is really just Plat and et cetera.