Quite late to this thread but I'm responding to the first post.
I totally agree when you say the classic era Touhou games have a certain charm to them, especially Imperishable Night.
Those older games also had quirks that made them cool. Things such as the songs being heavily tied and synced with whatever happening on the stage, especially in the extra stages.
Not only do the songs pump up in tandem with Midboss appearances or spell cards, but the backgrounds were influenced as well. Th8's stages 4 and 5 are great examples, along with Th7's stages 3, 4, and 6.
The choice of instruments in those older games are also a big part of what puts them in a bubble.
While the newer games have similar instruments, they definitely change from Th10 - 12, and especially from Th13 going forward.
I'm also a fan of the Extra stages always showing a picture of its boss in the spell card background, something, unfortunately, dropped in Th12.
Finally, the dialogue in the older games was just funny as shit. Th8's Yuyu team and Marisa's team, all of Th6 (English Beef, Smug Reimu, Asshole Marisa). I don't really play for the dialogue/story, moreso gameplay, but the few times I have read, it was great.
Despite my love for the older games though, Th11 is probably my favorite. I don't even know what it is. Probably just the amazing variety of shot types, music, and progression. Th14, 15 and 18 are great too. I wasn't expecting Unconnected Marketeers to be as great as it was. Endgame Th15 is just brilliant. Clownpiece and her stage have amazing visuals and music sync, and Junko's fight is just amazing depsite the Danmaku looking quite simple, but it matches the theme. Disappointed that the game had Overdrive cut.
Double Spoiler and Impossible Spellcard were sick. Fitful nightmare is just...Fitful nightmare. That name would be cool as a game actually. Touhou 19: Fitful Nightmare.
I never played the fighting games, but all the sprites look incredible.
I'm fine with the fanbase being the size it is honestly, as I feel with Cave Story. It's just a small bubble of passionate people who enjoy this one hyper-specific niche.