Wikipedia links from the Touhou Project to an interesting article, called "database consumption", where people are fans of the component parts of an original work, but want nothing to do with the original work itself.
https://en.wikipedia.org/wiki/Database_consumption
It gives the example of Hatsune Miku, who strictly speaking is a fictional character attributed to a sampled singing voice in a vocal synthesizer VST called Vocaloid 2. She was the product branding. There is now a huge industry of fans inventing stories about Hatsune Miku and rendering/drawing pictures of her and enjoying thoughts of her being their waifu. Whatever they've made up is now their headcanon.
I can totally understand Hatsune Miku fans asking you to get lost if you tell them you bought Vocaloid 2, it's cramping their vibe.
Is it the same with the menagerie of Touhou characters? Are there people enjoying thoughts of Marisa Kirisame who don't want to be reminded she's a character in a shoot'em'up?
Due to how Touhou is liberally licensed, there absolutely are people who are fans of the characters/story/music/fangames but have never played any of the actual shoot-em-up games. Within the community they're referred to as "secondary fans" since they only engage with the franchise through derivative works. I haven't heard of people who are hostile to the idea that Touhou is a shoot-em-up franchise though.
Is this the first "not even wrong" moment for me??? Why would Miku fans not like someone using the VL2? It just makes no sense...
ZUN is hostile to non-Japanese people plating shmups because he doesn't imagine that racially handicapped people can play such a challenging genre. I'm barely being facetious. Western fans are opposed to buying the games because of that. Why play the games at all if it bothers you so much, fair question, it's not like there aren't better games from that genre. I always pirated them but I pirate everything anyway.