The ranked system is working fine in regards to "streaks".
Say you're some Silver III (S3) player on a win streak. You keep playing to climb, hopefully to G5. How can you demonstrate that you deserve to climb if average skill of your opponents and allies remain the same? Hint: you can't. If you can consistently win games (in theory just by winning over 50% of them) with worse players on your team, you've demonstrated that you do not belong at your current rank, but higher. Same goes for consistently winning games with better players on the opposing team. Say you're S3 on a 15 game win streak. It doesn't matter if some of your allies are S5 versus S1 enemies or some allies are S3 versus G5 enemies - some of your allies are expected to lose. Why? Because with your current MMR, Riot thinks you're able to win games and make up for your team's deficiencies. That is in fact what you've been doing for many games now. To test to see whether you deserve to continue climbing, they need to either pair you with allies who are worse or pit you against players who are better, or some combination of the two. I see a lot of people crying about how some of their team mates they get are worse when they're on win streaks. You'd be crying just the same if the enemies were all better than you for being on a win streak.
Individual games do not have to be fair. Say you're S3 and the rest of your team is S5. The opponent's team is also ranked the same - 1 S3 player and 4 S5 players. If you're mid and stomp the opposing S5 player as you SHOULD, it shouldn't be surprise to you that your S5 top lost to their S3 top. Now since you're the highest rank player on your team, you should aim to out carry their highest ranked player. So even if you're 10-0, the enemy S3 player might go 15-0. Now how do you figure that you "deserve" to win, and therefore the enemy S3 player "deserves" to lose? If you think you "deserve" to win, then this game isn't for you. In fact team games aren't for you - go play Street Fighter where you can 1v1 and not worry about 4 other allies to perform well.
For those of you who think that Riot will only gives you bad allies instead of giving you better opponents (I've seen people make this claim in a certain mass-upvoted thread recently), you can look at high elo smurf accounts to see that is completely untrue: https://na.op.gg/summoner/userName=neaceplank+soloq If you go to games 4-5 days ago, you will see that he was G5 vs low Plat players, i.e. against better opponents. As he continues to climb, matchmaking is not suddenly throwing in G5 allies versus P5 enemies. His allies are P3, his enemies are P3.
There are some things that should be improved on for matchmaking. Streaks making your games harder to win/lose is not one of them. Overall, it is working as intended. Now stop complaining about useless things and try to actually get better. There's so much free content out there for improving. If you're S5 after 200 games, it's not your luck, your bad team mates, Riot's faulty matchmaking, etc. It's you and you deserve to remain S5 until you get better/worse.