This is not exactly what I see. For a start, 2 years is too much of a short period to actually make any sort of analysis about the industry as a whole, Vn development usually will take quite some time, so much that most full price titles released would had its production started before COVID. Besides that, I have no idea of what Vns with 1-2 h-scenes you are talking about. While there had some producers trying to cater to the western market, they are in the minority, the majority still releases with the japanese market in mind first and foremost.
I don`t follow what you mean by DMM style games with high art quality and short scenario, but if you are talking about single heroine games, those have being a trend for quite some time now, and they usually have a high amount of erotic content. While some studios focus on this type of content, others seem to have used those as a filler between higher productions, so it`s not that much of a big deal.
As far as high-production goes, seems to me to be unfair to use majikoi as a standard for high profile VNs, that thing is not normal under any circumstance, the amount of voiced characters with high profile VAs is not a common thing. As a comparison with majikoi, wagahime was release just this year, and I wouldn`t say to be lower as far as productions goes. Gikei, like all inre games has pretty high quality productions and it`s pretty long. Buddy mission is both long and have Murata, the artist of One punch man doing the art. Fuyukuru, being under silky`s plus brand, certainly have higher production than any of the previous sci-fi season series of watanabe. Upcoming titles like hentai prison or the Aokana extra2 have fairly high production too.
Plenty studios still do long titles, you just doesn`t have as much of the unnecessary long titles like 70h long novels, but this could very well being because if they were supposed to be this long, they probably will end up being broken on multiple games anyway.
Again, 2 years look too much of a short time to actually make a big analysis of the impact of covid in the production of VNs.
