Oh look, yet again alluding to the map being the underlying reason…
You see, the “skilled players” prefers easy wins. Means better rewards for a lower amount of effort, and faster as well. So as soon as premades got mitigated, they moved over to WSG and later on AB, whereas there’s no way to know the win rates on the server side, even though you claim there’s a statistic (even though you literally made it up out of thin air). Simple truth is, the win rates depends greatly depending on who you ask, in those other BGs.
It’s not like all of the tryhards quit AV when premades got mitigated, but it created a chain of events where the ones left queuing became so few that they were too thinly spread out, so the same ones that were excluded from premades while it was still possible and the “casual” premaders were the majority of the ones still queuing for AV on the Alliance side.
Which in turn created a feedback loop. They were too bad to win, so they quit trying, and then because they weren’t trying they lost even more so they quit queuing, and on and on it has continued ever since.
A better way to fix the endemic mindset issues is to just disable automatic matchmaking for teammates. Forces everyone to be a premade, all the time. The better ones will win, the worse ones will lose. Regardless of faction.
It even fixes bonus problems like bots, AFKers and so on.