Coming in quite late, but I think the main reason for QoV's fall (and maybe the reason that it isn't dead) is that the game was broken by the dev team in such a way that you have to make an effort to play. Want to use your strongest team? Sorry it probably has the multi-hit ability which will lock the game. Like playing with sound on? Then enjoy having to restart the game every time you find a valkyrie as the encounter music eternally loops over all other sounds. In for the silly story? Until a few weeks ago at least, chapter 4 was showing its text in japanese here. Want to level and become strong? QoV's way of handling power is based on getting valkyrie drops and farming event units/exp, but the last event was in... June I think? This ends up transforming the game in a weird grindfest.
I really get the impression that its only up because they know that would make those problems more visible, so it feels like they're waiting silently for people to forget about it. I really don't want this to happen to some other games like MWA (I might be terrible at it but I kinda enjoy seeing gameplay discussions here and MWA and IWZ seen to concentrate most of it). Though I really wonder if we can do anything, as most of the few messages the QoV discord gets are about the freezing bug, mostly asking for fixes and we've got nothing at all yet.