Hello,
While it is true that carrying in bronze/silver is hard(er), I think you're misinterpreting what they said; I'll explain.
In lower elos, what lacks the most isn't insane mechanics or anything, it's decision-making. And maybe map awareness. And possibly communication.
So for a Master, if they take the best decision, the best engage, at the best timing possible, it doesn't mean anything if the team doesn't follow. In lower elos, the best decision isn't always the best decision, which I know seems wierd, but it's as it is.
The ranking system -although I do agree it is very flawed for other reasons- works on a average skill. You get to your elo after hundreds of games, not after 10 placement games. This Master person you mentionned would go back to Master even if they were to start back at bronzeV, it would just take them a bit more time.
Also, I would like you to explain to me how higher elo players (DiamondI's, Masters, Challengers) always seem to "luckily" get back to their rank, if as you said "it's rigged" and "rank mean nothing" ?
I don't want to be mean, but your opinion is very likely to be related to you not understanding the game fully, which makes you lose more games for reasons you don't understand.
It's just a suggestion, but I think you would have a lot to gain from watching some high-elo streamers who commentate their gameplay, in order to improve globally. You'll see all that they are doing in ranked which you don't, and possibly you'll find some reasons as to why you "can't carry in silver"