Some people just love to bitch, especially if that's all they do. James Wallis said (IIRC) "Game designs aren't tools, but some game designers are".
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Humor, jokes, memes about TTRPGs
It is a little weird that D&D is synonymous with tabletop RPGs, considering how many other great games are out there; especially these days. But D&D is by no means a bad game and people should still play it.
No one complains more about a product than long-time fans of the product. They're the ones who have had the time to feel betrayed by something, be it minor design choices, or things the owners have done, and who also feel a deep sense of ownership over the product.
Haters are just fans that feel alienated somehow, and can't move past it.
I've literally never heard anyone blindly hate D&D on Tumblr. There are a lot of complaints, for sure, but the biggest blogs there post about how D&D is fundamentally a game about dungeons and not meant for other things, and most of them celebrate the system when used right.
I imagine that Brennan Lee Mulligan walks a fine line as a public figure.
He still plays D&D often enough to (seemingly) not alienate people at Wizards whose work helped launch his career.
But he also plays significant amounts of other games, including some that I think are Indie developers, like Kids on Bikes.
I'm sure he's aware of the issues and concerns in the community around D&D under Wizards - and probably shares many of those same concerns, as a fellow player and DM.
But, yes, the idea that Brennan secretly hates anything sounds pretty silly. Brennan has been pretty direct with his epic rants about things he really hates.
I'm pretty sure Critical Role has also done some Monsterhearts stuff, which is also indie. I don't personally like that game for a myriad of reasons, but I do believe Mercer ran it one or two times.
I'd like to find those folks, but tumblr is such a mess. Fortunately bsky is not that bad. Point being, it's hard to find platforms where the elephant in the room isn't felt so much. Even lemmy is dragon town all over again.
On Tumblr (and LJ), the indie devs get to be honest about their feelings. On BSky, it's all advertising. Because I'll tell you this - every dev who's not part of Hasbro despises them. So do most players.
I sure did not learn anything about ttrpg development or even what cool indie games I could support from following them, because all they do is complain about D&D. If you are D&D hate blog a) jsut say so instead of pretending to be something else and b) you are a D&D blog. Being defined by hatred of the thing is still being defined by the thing.