Very well said. You articulated a lot of my worries as well.
I think another part of The Walking Dead's success, beyond the popular franchise, was that you were playing as original, relatable characters and responding to situations that were designed from a somewhat realistic perspective (ignoring the zombie aspect). I don't think that Telltale replicating the gameplay of The Walking Dead would work as easily when Telltale is working with characters that are already established in a franchise that are dark, adult representations of fable/fairy tale characters which are less relatable to players than the characters of The Walking Dead. Furthermore, since it was stated that Fables will be canon to the series' lore, Telltale will not have as much freedom to deviate with the different choices characters will make in order to tell their story.
Furthermore, I also feel that this will deviate Telltale from their plans to release games quicker or even simultaneously. By choosing to adopt The Walking Dead format for their future episodic games, Telltale will spend longer amounts of time for each episode, which will likely be a bad move considering that Telltale is also moving more towards larger fan bases that will lack patience or understanding during the wait for episodes compared to monthly episodes.
The Walking Dead worked so well not because of the story, or because the puzzles were "easy, but not too easy" for casual gamers. It worked because the gameplay gimmick was a great match with The Walking Dead as a franchise, since The Walking Dead is all about the choices people make. I don't think the gameplay format should be shoehorned by Telltale into future drama/suspense games simply by virtue of having been a success in The Walking Dead, and to think that we could have possibly had Fables by now is somewhat disheartening not as a partial fan of Fables, but as a fan of Telltale for several years.
I think it's odd to see why Telltale ponders why their Wallace and Gromit point and click sold poorly despite being great, or why The Walking Dead beat out Jurassic Park by a landslide despite both focusing on story over gameplay. I think that if Telltale ever wants to make a huge impact on the masses, then they need to incorporate the good parts of adventure gameplay that work with the license they work with, and add some changes to "spice up" the adventure gameplay while also removing the parts of adventure gameplay that don't work with that license. Adventure games (as of now in my opinion) should not be a virtue of being hard/complex or easy/simple, but rather focus on how fun gamers can have regardless of difficulty.
What separates "cinematic" games from big companies and cinematic games from Telltale is that even though big companies remove gameplay, they still offer you control and freedom to do what you want and allow you to explore the universe of the game at your own discretion. With Telltale's earlier cinematic games such as Back to the Future and Jurassic Park, Telltale limited your freedoms entirely outside of minor variations from conversation choices or the likes. Even though story is important and can establish games, as clearly seen with the Walking Dead, Telltale needs to learn to separately prioritize gameplay and story instead of offering story as the main gameplay feature.
The Walking Dead, as I said earlier, shares much with Jurassic Park in that both focus on story. However, Jurassic Park was disliked by many because the "director's chair" gameplay gimmick barely fit Jurassic Park, only by virtue of Jurassic Park being a movie. I remember having a scene in Episode 3 of Jurassic Park where the player had two separate characters with their own motives arguing with each other, and the player was forced to come up with rebuttals for both, essentially having the player argue with themselves in game. However, The Walking Dead beat Jurassic Park massively because, as I said earlier, the "choice" gimmick actually worked with the franchise, and Telltale executed it in a stellar way minus lack of puzzles or depth. In Walking Dead, you weren't arguing with yourself; you weren't performing trivially pointless QTEs for the entire game. You were affecting the story, because your actions mattered, which was important for the Walking Dead; not because the Walking Dead was a drama entirely, but because the gameplay benefitted the Walking Dead in particular.