Every time I'm in my promo series I get the worst teams I've ever seen; This was my 5th series in b4

When I'm out of promo series it's normal-ish, 50% winrate or so. Some teams are good, some are bad, sometimes I do well, sometimes I don't.

HOWEVER:

Every SINGLE TIME I'm in promo series (in bronze 4 btw), I end up with the most brain-dead, ignorant teams I've ever seen. These people will dive 1v3 and suicide just so they can get a kill on the 0/2 mid lane instead of the 10/0 bot lane. People in champ select autolock veigar support when I want to veigar mid, then end up feeding 0/5 in the first 10 minutes. People don't know how to give up laning and ARAM mid when they are behind, giving more kills to jungle and their laner.

The last promo game I had, I managed to keep my enemy Ahri to 1/0 (I messed up once from lack of vision) for about 10 minutes. I'm immersed when I play, so I generally don't look at other lanes unless I'm going to roam there. I look up at the scoreboard to check my FPS and suddenly I see "1 vs 9" after 8 minutes, and it takes so much energy for me to not scream and start flaming in chat (which I'm already under a 10-game restriction right now so I can't). After 15 minutes it's 3 vs 21, where our Jhin has 2 kills and I have one. There was no way for me to roam bot because our bot pushed up all the way with no vision, then question pinged the jungle when their Udyr comes and gets a double kill. And then when they finally surrender their lanes, they proceed to chase everyone down only to die. Our shyvana tried to dragon onto the Ahri... when shyv was at 20% health. So our only hope of eking out mid towers is gone because they feed the laner I worked pretty hard to not feed.

It's only during my promo series and it's so frustrating. None of my friends want to duo with me either when I'm in promos because they KNOW that this happens all the time, plus they think it magically screws up their MMR.

And this is NOT just one bad promo series. I have had a grand total of five promotional series over this season and the last month of S7. Every single series I end up with terrible teammates. And yes, there's the occasional game where I do poorly, and I blame myself for that, but I DEFINITELY think I am playing to a higher level than bronze 4 and my teammates are sometimes holding me back, in terms of the promo series only.

And yeah you can say "nope, it's all about your own performance, you could have done something." But it's not. Because one feeding teammate can ruin the whole game. And in this case it was three or four. You can only do so much when four enemies are fed. It's just so frustrating because I KNOW I can play higher than b4 but it feels like either matchmaking or just dumb luck is trapping me. I've tried focusing on my own play and it's helped a lot in terms of dying less, capitalizing on opportunities, and getting more CS, but it doesn't help singlehandedly carry the game.

This was a vent but I would appreciate advice on what I'm doing wrong. Thank you.