It's a statistical measure telling that under the influence of your play...
Not really. I mean, it is, but at the same time it's not
This is a team-based shooter we're talking about, and the teams that are really capable of dominating in a team based shooter and going to be made of players who work together as a single unit, understand each other very well, have specific strategies and tactics practiced with one another, etc. A team of "individually skilled" players randomly thrown together are never going to be able to out-perform that consistently. Teams are what's important. It's also why solo queue is considered a joke compared to party teams in online gaming in general.
While there is always a solo queue "meta" and you can do things that are going to help you win on average over time, those things are almost always sub-optimal and simply abuse the fact that both teams are disorganized. It's rare that any of it will ever work in a
real match. Meanwhile, the member of a strong team is going to be a flat out better player because of his/her ability to win as a team, but can't (and shouldn't bother) bringing those things into a solo queue match because there isn't a chance in hell that random's will be able to be good teammates with it.
So why am I saying this? While it's true that an individually skilled player can earn a well-deserved high rank in solo queue, people that can't earn that same rank aren't necessarily worse players because they are quite possible capable of being way better in
real matches instead of sub-optimal solo queue.
An A+ in solo queue means that the player is strong enough to get A+. Being "stuck" out of A+ means nothing. Nothing. Nothing. Nothing. You can't infer anything from it. Period.
It's not that I think you disagree with this, I'm just stating this to the general public. People will defend what they like, and people feel the need to defend Splatoon's ranking system (that doesn't deserve defending) to the point where they will down people's ranks in lieu of what they could do in party teams, which is flat out naive.