Here's my thoughts:
Take a Platinum player. Put them in Silver V.
Compare the rates of climb when they get reset to ~ Gold II on new Season placements vs the Silver Climb.
It's likely going to take them 200-300 more games to climb 5 Brackets on the Silver than their Gold II.
Why?
Silver V is like a Lottery. it's not about skill, or discipline, split pushing OR team play. It all goes out the window.
Even if you have an illusion of skill in that elo, where your team dominates 25 to 5, that's usually all it is. An Illusion. Some or a couple on your team managed to get a very early First Blood/snowball, and create the illusion of a skill match, supported by gear and the charisma given to a team by a lead.
And no matter how skilled you are in that elo..... a lottery team results in situations where unless you're playing a perma reset champ like
..... you still at best barely pull 50% win rates, even if you historically have 65% Kill participation and a 8 KDA.
The problem arrives from the fact that literally 55% of the population is in Silver, and about 20% are Bronze. About 75% of the community isn't actually learning game proficiencies. They are playing by impulse/for "fun." and many just play retaliatory toward teammates who offend them.
So..... technically..... in some cases.... Yes. Shitty teammates do prevent climbs. However, in some of those cases, it's also the complainer.
I've been Plat II or better since Season 4.
But..... I have 3 perma bans. I've had accounts start at Silver/Bronze to insufferable placements. Whereas I can go Gold V to Plat IV in about 100 games, Silver accounts I sometimes don't even get up to Gold in 300-400 games, because gameplay in silver is entirely different than in Gold or Plat.
Plat: Quick to take advantage of team mistakes, but generally cautious lane phases, and laners help ward for junglers. Routinely buys Control Wards, and tries to keep early game deaths to a minimum. The game usually doesn't break out until after about 12 minutes.
Gold: Usually quick to take advantage of team mistakes, but often gets caught in Yolo lane skirmishes which starts a lane snowball. However, Junglers usually help compensate and minimize that poor decision making, softening it out. Covers junglers about 70% of the time. Buys some Control wards, and tries to keep game deaths to a minimum..... until the snowball starts. Game USUALLY doesn't break out until 10 minutes, but often drives hard to end the game once it does. Hard to stop the snowball.
Silver: No one's really taking advantage of team mistakes. Instead they make a contest of who can make the least mistakes. Often gets tunneled on farming or pvp, or on base defense, but not all at the same time (Not multitaskers). They ward for themselves, or don't ward at all. They don't usually care about protecting a jungler at all, but still expect the jungler to be in their lane at all times. Junglers do not know how to use Drakes/objectives for the most part. Bot laners don't know that Drakes are team objectives, and almost ALWAYS recall when a Drake window arises. Buys about 3 total control wards a game. They view deaths as inconveniences but don't ever try to avoid them. Almost all chase kills, and the supports/tanks often die in the process of trying to save the chasers.
Game often breaks out within 6 minutes, which sabotages cs rates, stable lane phases, and unless you are a hyper reset champ on a smurf, generally creates an entirely different game dynamic that's hard even for smurfs to adjust to. This means one team's adc is almost always useless because it takes twice as long to buy their first full item, which means csing is far less reliable. It means support's Levels are crippled by their adc's performances. It means Jungler's CS gets taken over by laners who care more about padding their gold than the fact they are bullying their own jungler's gold supply. It means almost all drakes are 1 team endeavors, because the losing team doesn't have enough pressure to even create a skirmish there, and the team's are usually not interested in congregating anyways.
The only real difference between Silver and Bronze? Silver players have moderate reaction times. Bronze doesn't react at all, and often freezes in place not knowing what to do.