When I watched that video, League immediately came to mind, as its ranked system has been heavily criticized for many of the reasons mentioned by EC. I generally love Extra Credits, and I think they did a great job here of explaining how porting single-player ranking systems to multiplayer is innately conducive to frustration. That feeling, justified or not, that one is not as responsible for one's losses as one's own teammates is at the core of the frustration many players feel with Ranked, and I suspect is also a major source of toxicity, as that kind of mentality innately leads to playing the blame game. In this respect, Riot's method of curbing player toxicity mainly by punishing outbursts in chat, rather than by addressing these problems at the source, have likely compounded the issue further, as many players who got chat restricted or banned for their attitude in chat express a feeling of being trapped in an inescapable ordeal with the matches they played. As such, Riot needs to find a way to bake in teamwork as a clearer incentive to players in Ranked, particularly since the upcoming changes don't really do anything to solve the issues mentioned in the video, or by many other players.
Personally, I think a core problem with ranked ladders, one that the EC video doesn't entirely discuss, is that ladders themselves are ultimately zero-sum, even though one doesn't want it to feel that way as a developer. At the end of every season, a certain number of players will be Bronze, Silver, etc. all the way to Challenger, and based on the breakpoints set, these numbers are pretty fixed. Therefore, when someone climbs up a division, it's generally because someone else got demoted. This is one of the reasons why the climb can be so frustrating, because at the end of the day, half of the total League population is going to end up missing on the Gold+ rewards, and so by design. This is where EC suggests good solutions, namely by offering rewards just for playing, and keeping those rewards even if a player got demoted.