@musou-tensei I like the story and characters in Touhou a lot too. The first Touhou game I played though I didn't know about the characters, I just saw there was a crazy looking bullet hell game that I wanted to try, and then my interest in the characters followed the gameplay.
It's funny looking back at my own post, where I said
Dungeon crawlers and Bullet Hells are the two genres where I think it matters the least to me.
when now I don't think that last part is true. A new bullet hell game would have to pull me away from my devotion to playing Touhou, and since I like the entire package of Touhou (story+gameplay), a bare bones bullet hell has a steeper hill to climb to get my attention.
The same is true with Dungeon Crawlers, where I've got my plate full of Etrian Odyssey games and some other favorites (and not enough time to play them all!).
So I think what I meant to say there is that those two genres have the easiest route to making great games without having a lot of story, in contrast to some other genres. But once an individual becomes wedded to a favorite series in any genre, what then? They're invariably going to feel invested in all the story and character elements, and any potential new series would have to overcome all that to pull them away from it.
This is making me re-contextualize @The_Andredal 's original question. "How much does the story matter in singleplayer games?" If we're talking about the satisfaction of playing and beating a game with all other things being equal, then my answer is that I think good gameplay is the most important piece, but having good characters and settings in addition to gameplay matters to me in almost all cases, while "story/plot" is less important.
But if we're talking about "how much does it matter when new games are competing for your attention"? Then I find myself thinking in terms of the limited time I have available and what games/series I already want to play in that genre. And often when I am comparing games in the same genre, it isn't clear cut to me which one has the better gameplay. So characters and setting become bigger factors, and my pre-existing favorite IPs/series can become huge factors (which sort of falls under the "story" banner).