過疎

kaso
to suffer from a (new or existing) lack of popularity, particularly as a video game

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I had only ever encountered this term in reference to discussions of Japan's rural areas, where it refers to the depopulation that occurs as younger people move away and the older remaining residents gradually pass away. But I encountered it in metaphorical use today, to refer both to video games that never attracted a fanbase to begin with, as well as to video games whose players depart (depopulating the fanbase, as it were) once the game has been played through.