Ya I get those too. I reached B2 promos a couple days back riding a decent win streak. Then after that I consistently started getting the worst teams imaginable. I could no longer carry and I'm currently a couple losses away from B5 for like the 10th time this season.
Thing is OP, it's not because of having bad teammates or feeders or any shit like that. It's because I cannot carry well enough to win with the most terrible team mates. Smurfs carry these idiots all the time. You will come across a couple smurfs, either on your team or the enemy team and you'd see that it is indeed possible to carry yourself out. Smurfs would usually go something like 17-0 or 30-2.
The thing is, it is really not easy to get that good. Don't listen to people saying Bronze is easy or Silver or whatever. It's not. Even getting to Silver is a huge accomplishment. You need to understand that. It's going to take you a massive amount of effort to learn how to carry Bronze or Silver or whatever rank you're at.
If you're Bronze and want to get Silver or Silver aiming for Gold, don't expect to figure out how in a couple months. It's probably gonna take you 2 years at most to get good enough to reach the next tier. I've been playing consistently for about a year and a half and my best is B3.