There's a problem in equating Clan Battles to Stars. Namely that Clan Battles are not considered "fair matchups" and there is a weighting to the Point Gain/Loss depending on the Advantage/Disadvantage assumed in the matchup.
Example: A Typhoon 1 Clan Team is matched against a Storm 1 Clan Team.
If the Storm Team wins, the Typhoon Team loses MANY Points, and the Storm Team gains SOME Points.
If the Typhoon Team wins, the Typhoon Team gains FEW Points, and the Storm Team loses FEW Points.
In other words, the gain/loss is dynamic to the matchup/situation. Or said another way, every team is at a different position, so every outcome is weighted differently.
This is not how Ranked Leagues work.
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ALL Players in Silver... are Silver. While you may recognize someone as Super Purple or Super Red, they are all "Silver". Why? Because as far as the Ranked Battle league is concerned, that's how far they've come in the current Sprint/Season. If they want to be higher, they should push for Gold. If they didn't want Silver, they should have avoided finishing Qualifiers and waited for the Sprint refresh.
The experience you have isn't a full SBMM "skill number vs skill number" system... you have a Random Battle queue that only includes players from the League in question. So you are using the same situation as exists in Randoms to differentiate yourself and influence a team to win.
Is it possible for poor play to keep a player in "Elo Hell"? Temporarily, yes. That's the nature of Randomized Matchmaking. However, in the long run, no. Consistent performance will overtake the odds and place them in your favor, because statistically higher-the-average play will result in higher-than-average Win Rate.
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This can be explained in a few ways.
1) The average skill of Bronze is equal or lesser to the skill of that player.
-- Which seems unlikely due to such a poor win rate.
2) The small amount of sample sizes needed to get through Bronze and Rank Out allows for Outliers and "Carry-Throughs"
-- This is entirely possible as a few Win-Streaks from lucky matchmaking could certainly result in a trend that drags the player up and sees them Ranked Out
Similarly, the "Carry-Through" could have happened in the Silver Qualifiers as well as only 5 Stars are needed to advance.
Silver has more Stars overall needed for Rank Out, which makes a significantly below-average skill (for their current league) more unlikely to be able to Rank Out/Advance due purely to Luck/Team Draw.
Gold has even more still, which makes it even more unlikely for "Carry-Throughs". However, there are legends told of people grinding hundreds and hundreds of games in high-end Ranked Battles to eventually push through and Rank Out.
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There have been multiple ideas floated as to how to avoid such issues.
Base XP being related to Star Earning
Lowest on the Winning Team doesn't Earn a Star
Losing Team cannot "Save" a Star
Limited Attempts during Qualifiers
Limited Attempts during Sprints/Leagues
The larger issue is that this is a game, and while having teammates that can make you question if you are, in fact, not dreaming... it's still just a game. Ranked is there to be played, and the better your "A Game" the faster you move up and Out.