The diagonal is undeniable. Clearly the higher the play count, the better the rank becomes for most players. More than half of the rank 1 players are in the final and largest playtime group and more than half of this group is rank 1 or 2-5. So Stawek indeed seems right, casual players with only a few games a day won’t rank out and most of them are on low ranks.
However more can be said on the low and mid-end. Rank 10 was reached by large groups of casual players, proving that it’s possible with even 1-2 games a day. Rank 6-9 is practically evenly distributed among the battle groups. If we only know that a guy is rank 6-9, we can’t guess if he plays once a day or all day. There are 500+ guys who managed to reach the same rank as I did by playing 5x more battles.
So this post wasn’t as definitive as I’ve expected. I can’t say “ne-ne-ne-ne-ne-ne”, nor I can say “yes, you were right”. It’s somewhere in-between. The conclusion is at best “you need to play a lot to have good rank, but playing a lot doesn’t guarantee you get there”.
Probably the main problem here is self-selection. I mean if someone fails to progress, he’ll likely give up and go back doing randoms instead of keeping trying. We can’t just force every player to play ranked no matter what to determine how many would still be worse than rank 15 after 200 games.