I think the other D&D game that came out recently (Dark Alliance) is probably a better example of devaluing the brand.
Only the D&D universe allows for games like the BG series or Torment. It's all about the lore.
Let's make no mistake, D&D is all about the lore. The RPG mechanics are pretty generic. You have thousands of cookie cutter rpgs out there (especially jrpgs) with complex and interesting game play mechanics that are largely forgettable. D&D is still relevant not because of the game play mechanics, but because of the lore. And this lore was not really used very well in Honor among thieves.
Maybe you're right though. The D&D universe is specifically designed to support complex narratives and generic ones as well. Though for honor among thieves with the D&D name featured so prominently in the title I'm sure most people unfamiliar with D&D walked away thinking that D&D was some generic fantasy universe. D&D Lore is better, deeper and more complex than GOT or LOTR by a huge margin. It's barely comparable it's like comparing GOT with the Harry Potter universe.
I think the thing I enjoyed the most about Honor Among Thieves was how the different characters were manifestations of player archetypes. You have the master planner, the strong and silent, the high-level lawful good guest player who the DM sets up an extra-hard challenge for, and so on.
Season 8 of Game of Thrones.
The spin off was alright but I didn't really care enough to keep it up, and I get a lot of people didn't. LOTR comes to mind too, ditto for a lot of the "slop" that Disney has been pushing for Star Wars.
There is a lot more stuff out there, and most of it isn't great, so Ima tune it out until the test of time determines if it's worth it.
It's hard to describe the effect. Essentially this is what happened with LOTR.
Also take for instance the recent D&D movie which was just ok/slightly good. The movie cheapens the D&D IP, while something like Baldurs Gate builds on it.
Maybe from a business perspective it's the most profitable move but for the original subject the IP was centered around, whether it was books, games loses the charm if the movie sucks and Hollywood churns out shit movies for a quick buck really fast.
It's not always bad though. While Marvel did well, DC did not.
It's weirdly irrational but that's just how people behave.