on a side note: as someone who more actively follows the jp touhou scene way more than the en one these days
i don't get the fuss about sopm. even when it came out i didn't think more than a small handful of people cared. characters are contradicted continuously in this franchise and fans haven't exactly stopped from interpreting them the way they like one way or another. and people definitely like the new games' content. (i quite like the casts of ddc/llok, personally, and i was not a big fan of ufo/10d)
people like to make up a lot of pointless drama where there really isn't any because it's more fun than thinking people get along fine, which they do, so i think people are drastically overrating how much various 'factions' exist and fight. people take what they like from it, ignore what they don't, and move on. touhou's a very, very diverse franchise with a little something for everyone and zun's own attitude of not taking it too seriously pans over to fans interpreting things how they want.
also, like, kancolle taking a large portion of the population is more a blessing than anything else. some things to note:
* the population that kancolle took is one that drifts from Big Thing to Big Thing, and is also generally an audience that was drawn in not by interest in the franchise or its setting, but by memes, videos, and doujinshi-related content. wouldn't be surprised if kemono friends took a big chunk out of it this year.
* ... and, of particular note for disappearing fans: porn.
here's a chart showing a breakdown of tables by franchise at c91, blue bars are 'for all ages,' red bars are 'for men.' (green is 'other' so i'm assuming 'for women' and 'not for human consumption') top row is kancolle, second row is touhou.
* ... which, you'll note, touhou is
still the second most popular franchise by doujin content at comiket, either in total or when counting only all-ages works, and has not shrunk at all from c90.
so, touhou as a whole is distinctly *less* oriented towards a certain breed of otaku now, which has opened room for far more diverse creators and interest in the actual touhou franchise than had existed even during touhou's peak. i see a lot more women involved now than i did even a few years ago! it's actually really nice to see, honestly.
the franchise is not dying, it's showing surprising health and resilience. y'all need to chill out and enjoy your silly frilly dress girl series more casually. also: play more iamp.