To give a bit of background info:
The Rares List was retired following public vote and discussion a year ago.
Among other things, people had voiced concerns that the list was outdated and no longer accurate to the values of the pets placed on it (or pets not placed on it, for that matter), and that it had become increasingly common for people to ignore list placements - in the end, the result of the poll was that people overwhelmingly either agreed to get rid of the list or restructure it, so the original rares list was closed and retired as a result.
You can still find discussion and links in the old list thread itself if you do want to read up on the whole thing in its entirety (beware, we blabbed about it for literal hundreds of pages), and can find various projects, including the one axelandria linked, by browsing the CS Chat board.
We also got an official rarity update at the start of 2019. The aim of this update was to reflect pets' rarities more accurately by moving the thresholds between rarities so as to combat the issue of too many of them being clumped into the same few tags.
You can find the official announcement here:
Forum/viewtopic.php?f=16&t=4014755(And yeah, fun fact, this update was one of the many catalysts that led up to the list retirement, as it revealed there were OMGSR pets stuck as far down as the September list and brought the issue of outdated placements to the public eye again :'D)