Assuming you want an honest answer, philo, I think there are three major obstacles to this community flourishing:

1. Vague/misleading images - Many of the starting images are vague enough that they could apply, for instance, to over half of the thrash songs from the past two decades, whether obscure or well known. Others are almost adversarial with how far they stray from the source. A recent example is the prompt for "The Lady in Red," which prominently featured a beautiful young woman... in a silver dress. People who are interested in guessing can easily become discouraged when it seems like the game is tilted strongly against them. Many won't hang around to figure out how to create their own posts if the game seems unfair.

Suggestion: Make an effort to weight prompts in a way that adds some degree of emphasis to bits of the lyrics thar make a song unique. In the event a particular song is more obscure or niche, provide some level of assistance either at the outset or after a set amount of time. This could take the form of the decade of release, an additional image that highlights other specificity in the lyrics, or even a witty hint about the artist/band.

2. Unfamiliarity with prompting - I get the sense that there are many who are intrigued by the pictures and the concept but do not know how to create images that they feel accurately convey the song lyrics in a way that is guessable. It can be frustrating to feel like you're stumbling in the dark without much guidance. Some thrive on discovering things for themselves, but I'd say the majority probably abandon their attempts once they feel like the price of engagement is sufficiently high.

Suggestion: Increased availability of information about how to prompt successfully. Providing assistance and advice when asked for it.

3. Your attitude - Without regard to any justification there might be, you often come across as prickly and unwelcoming. There have been times that the community has seemed to be less of a cooperative space and more of a power trip. People who pass the first two obstacles may be turned away by the overall atmosphere here. Very few will want to play against the actual challenge, the added difficulty of vague or outright misleading images, and the nagging sense that the community leader is an active antagonist.

Suggestion: Less iron fist, more silk glove. In TTRPG terms, the DM shouldn't be playing against the players if they want to create engagement.

None of this is meant as an attack. This is my honest opinion of why this community is relatively inert, and some thoughts on how it could be invigorated.