You have the statistics to make a point to support. Tell them with numbers, that it looks like something is going very wrong. That the algorithm is not working as expected and overdos the boost for new games in general popular sort to the point of pushing actual popular games out of the loop. Maybe added in with some other stuff that seriously mixes the games so that "popular" is now a lie and should read "random and new". There already is new&popular sorting. People expect some resemblance of actual popular, if they see popular sorting.
Of course I can not tell how the thing works, but I do can tell that your game is not considered to have had any major update in the last 30 days. An update is not automatically a major update and frankly, with 4 years in the making I serously doubt, that you have had like 50 "major" updates, if you update every month. But this should not be enough to push you so far down.
If you combine several tags, so that you have smaller set of games, it looks more plausible on the other hand. Adult, Dating Sim, Erotic, Harem will give a list in popular where I fully believe that the games above you are currently more popular than your game.
Should the sorting algorithm for one reason or another only consider small numbers, a huge variance in result is to be expected. I still speculate, that with their server moving, that there might be load balancing servers that do not properly report the access numbers. So games hosted on that one would report a lot less popularity. Or they might have changed the algorithm, so that visitors going to the game from their feed are weighed less, as they are recurring visitors.
Judging from the other thread, the only response you might get here, is, that there is nothing wrong with your account and that you should not rely on internal itch promotion. The fact that the game in that thread apparantly managed to appear last in list indicates, that there was or is at least one bug, but that might not be a software bug, as they were or still are moving servers.