>>715466502eroge in general is in a decline
you have a lot of movement from governments to verify consumers, block sales on some storefronts either due to morality or threat of credit card companies refusal to do business
crowdfunding as also dealt a big blow to getting more finished products (even though it has helped to put more options on the table with the caveat that those options aren't finished)
VNs declining make sense as newer generations move away from reading literature in general (with in increase of posts you see of people going "words words words")
there are more factors to it (economic, cultural, etc.), but that's just what i see directly