You'd have to remember your prior rank # for that instead of your %.
Well, people have stated in the discord chat that now being ranked at #80 isn't good enough to get into the top 0-1.9999%. Previously you could be ranked at the very least as far as #110 to get it from reports.
So one can extrapolate that the total PoC player base has declined by around 28% or so, I guess.
As for whether or not people have better teams... well, previously when I did up to stage 20 level 40, it got me rank 13. Now when I do it, it gets me rank 33 or so. So there's at least 14 new players (or more, to replace old players who leave) that now can get that far.
So I guess you could say the difficulty in getting to a higher % of PoC is a combination of both less players AND players having better teams.