For the grind, I wrote a lot of forum posts 'debunking' the myths. I'm not sure where most of you are at, and I can't read 200 pages anymore.
For the most part, a big part of 'working as a team' relegates just you to working with your teammates. It was a lot of spam for me. I started at 2800, dropped to 2600, and solo queued my way up to 3350. I found playing with people who didn't improve/progress as fast became tedious, frustrating.
If you're 'stuck' at a particular rank, it is because you're not good enough to carry out of it, despite the fact that you may be better than it. In that case, it is a lot of games to get to your actual ranking.
My win rate all the way to mid-diamond was 49.5%. I generally lost less SR than I won. I'm not sure if they ever became more transparent with it, but when I played, it was apparent to me that personal performance matters. I'm not sure if anything has changed since, so take it with a grain of salt.