DISCLAIMER I am not the best player ever, and I still have a lot of room to improve my self. The following is simply just my opinion on the system over all, based on recent games in the last few weeks. Hell if you check my match history, there are planty of games where I won my lane, and walked out into a mess of players that were way ahead, and started feeding out of control. There are things I my self can do to improve on this, and i'm not stating that I alone do not contribute to the losses, as I do on many occasions, i'm not perfect, but if I lose a game it should be because I lost a fair game. Not because I lost my lane, and then my team mates lost their lanes as well because they're matched with considerably higher rated players. ---- End of Disclaimer.
I've noticed this as well. Went on a massive win streak when I started playing again a 2 weeks or so ago, started in Silver 5 99 LP and got to Gold 5 in a week. Once I hit Gold, I noticed immediately that I hit a brick wall with the games. My teams would get loaded down with Silver 3 / 4 players, and my teams total MMR would based on OP.GG (Which I know isn't entirely accurate but something to look at none the less) be easily 100 to 150 points LESS than the enemies team, which was riddled with Gold 3 - Plat 5 players, and every single lane would get stomped into the ground, because its matching low / mid silver players against mid / high gold, and plat 5. I would end up going even in my lane, losing my lane or even winning, but when it transitioned to team fights, we'd just lose them back to back to back, and I'd go from a game where I left my lane at 1 and 0 or 3 and 1 to games where I end feeding because I can't do anything to any of the players that got fed by the other lanes.
There is no reason that i should get matched with players of lower MMR when mine is getting rated higher because of a hot streak. It shouldn't happen to anyone. Instead of a system that seems to want to STOP your climb at all costs, there should be one that recognizes this, and places you with team mates with similar MMR, so the games are balanced.
Especially since the game has changed a LOT since earlier seasons. I remember when you could get fed to the point you could carry a game completely on your own back in the day, and this system caters to that. Riot has been tuning items and champions so they can't do it, because its unhealthy for the game, yet this system that caters to that form of unhealthy play, is still here. Its not good for competitive play, for a few reasons.
Its not a competitive game, when you match a team of 1300 MMR Silver players, against MMR 1500. Thats not fair competition. If I go on a hot streak, and the average MMR for a player in my League is 1500, but I have an MMR of 1600, I should get matched with players on my team who are ALSO on a hot streak and have 1600, or just regular players with a 1600 MMR, and we should face a team of 1600. THATS competitive play. 2 teams equal in skill facing each other, and as it is right now? It does not work this way.
Its literally a system designed to stop win streaks, in the most unhealthy way possible.