This is where we talk about what we perceive to be the merits of TYPE-MOON, and how we--for now--continue to remain part of this fandom because of (or in spite of) the aspects that are associated with the media these creators/this company produces.
I've done the math and I've been a TYPE-MOON fan for a solid third-and-some-change of my life, and upon this realization I thought to myself "Huh. I wonder why that is?"
Half of the answer is definitely attributed to me being part of the fandom, and by fandom I mean Beast's Lair itself. "I'm a fan because I identify as fan!" Real nice stable loop answer, jackass. But it's certainly true my relationship to that feedback cycle--however diminished it may be in current years, as evidenced by how my post-count's progression has slowed to a glacial crawl--from conversations held by the posters, and works created by said posters and off-site fans had and has gotten me thinking and reevaluating of TYPE-MOON's material, and the sum of the parts of said material. Of course, that doesn't explain why I became and stayed a fan in the first place, and God forbid that I stray any further from the original intent of this OP and put y'all to sleep.
The other half of the answer: Urban/Contemporary Fantasy with a setting that hits on a range of supernatural ideas and mythologies that expands from the far past to the distant future. T-M works also have an engaging power system and an approach to said system that usually makes conflicts that happen in the stories be handled with a generally attention-grabbing and -holding manner. Also, the dripfeed of of dropping hints and introducing concepts that may or may not be expanded upon in future works. Expanding upon new concepts/characters/etc. and reusing established concepts/characters/etc. make the setting feel cohesive even across different continuities. But fights and worldbuilding are for chunni-babbies who like to see things explode and imaginate about stuff, and while I myself am a indeed a chuuni-babby none of the previously mentioned stuff would have the lasting captivation that it does on me if it wasn't populated by some interesting characters that help elevate it all from being a pretty dope-ass Tabletop setting and into-----a story. If I wasn't interested in seeing how these characters are handled within this setting, and if I didn't like some of them A WHOLE WHOLE LOT JESUS CHRIST WHAT IS THIS LEVEL OF FONDNESS????, I probably would've jumped fandom ship years ago (and probably killed myself too, lmao.) Then, once interested in at least some of these characters, am interested in seeing more of them, and seeing them do stuff that may capture my interest. My faves engaging in some whacky hijinks? I'm down, if the hijinks are good and they're written well as they have said hijinks. My faves getting expanded upon? I'm also probably down for that.
This all works together to give an impression that the fantastical sides of these stories truly do take place in their own foreign culture, a realized fictional world, and one alien to contemporary society's sensibilities--and hostile to mundane humans. At least, when done well. Harry Potter's got the Wizard World; TYPE-MOON has the Moonlit World (a fanon colloquialism, but still apropos), and when an author or director is able to realize that Moonlit World feeling it's some seriously engrossing shit, fam. It makes one feel like they're about to embark on a dangerous adventure, and not 100% convinced that they'll (or rather, the narrative-focused characters) will make it through in one piece. Production values, music, and aesthetic make or break this, and its often to the works' favor.
Also, if things don't end up as good as you would've liked them to be, or as bad as you expected them to be, you can always trashtalk 'em on the internet...which also loops back into BL, as a community, helping to facilitate extended engagement with the franchise!
TL;DR - Good setting that can facilitate a great atmosphere, neat magic system with a lot of thought put into it--perhaps too much, depending on who you ask--decent-to-good-to-GREAT characters that facilitate the occurrence of these stories, a steady release of content to catch my interest and fuel my hopes and dreams of more Good Stuff From Some of My Favorite Creators despite T-M being cursed to seemingly always have delays of some sort when it comes to the release of IPs (although I remember back when we were lucky to get one T-M thing a year, those sure were some fucking doldrums, although that did force the fanbase on BL to get real creative about topics and fanwork), and decent memetic potential coupled with a pretty decent, on a whole, fandom make T-M a keeper, IMO.
That wasn't much of a TL;DR but okay
I like it. It's neat, there're some folks in the stories that I wanna do and/or see cool stuff, and even when T-M stuff is not-so neat there's potential in the future for it to become neat, so I always get pulled back some way or another.
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I had hoped to talk about some specifics, but my post ended up longer than I imagined or hoped it would, so I'd like to maybe do so at a later time!