>>49817015First, the game itself actually only runs on higher architecture phones. A lot of people just can't play it, period. Then it's fuckheug. Then it runs into the gacha problem of playing more than 1 or maybe 2 gachas just isn't viable, meaning it has to actively pry people off of the Fate one or Fire Emblem one. Finally, iirc, the game had some sketchy prices and fomo bullshit right at release, which cooled initial uptake and retention.
Finally finally, Gelbooru remains free and accessible to anyone that can play the game anyways. Frankly, it's impressive that it's doing so well.