I'm not sure I like the idea that challenge is even necessary for a game to be good or engaging. When I played The Walking Dead, it was never especially difficult. In fact, I'd say it's one of the easiest games I ever played. The choices ultimately don't matter that much, because the story is designed to snap back and reconverge every now and again. In spite of that, it was one of the most engaging experiences I ever played.
The reason TWD succeeds at this is because it was never obvious what it was doing, at least in a first playthrough[footnote]As much as I adore this game, it has negative replay value. As far as I'm concerned, the only way to enjoy it is to play it once and then never touch it again, as a second playthrough actively ruins the first one[/footnote]. The choices have a way of seeming impactful, even when they ultimately aren't.
In the long run, I think this is indicative of the direction that adventure games are going to have to take to remain interesting and relevant. It can be difficult to make decent challenge in a puzzle game where the only mechanics you have available are inventory and Myst-style minigames, but to assume that difficulty is the only way to take advantage of the medium is to miss out on a lot of possibilities. What makes games different from movies is not challenge, but interactivity. Challenge is simply one form that interactivity can take. I would like to see more games experiment with different interpretations of what "interactive" means rather than just attempting to refine what's already been done.
One example of experimentation gone right is the Ace Attorney series. I thought the Ace Attorney games had stupid stories and crappy puzzles, but they were definitely innovative and had a good, unique concept, something that takes the traditional adventure game structure and turns it on its head. Historically, these games tend to have items, and you either USE item on environment, USE item on character, or USE item on other item. Then along comes Capcom and asks the question: "Why not USE item on dialogue?". This is exactly what I mean by experimentation. No game had done this before. In the hands of a more competent writer (and if it'd been more forgiving about dialogue/evidence combos because stuff that should work doesn't always), it could've been amazing.
That isn't to say I want more games that play like Phoenix Wright. I mean, I do, but that really isn't what I'm getting at. I really appreciated this franchise for the fact that it significantly expanded on the adventure formula rather than just adhering to it. That is really one of Broken Age's biggest shortcoming. It does some new things with story, but nothing about the gameplay feels new or exciting. In limiting the game to an old formula, the developers also locked themselves into the old formula's shortcomings. Simplified verbs are certainly an improvement, but they don't help the game feel actually new, just... old but a little less clunky. They certainly don't solve the biggest problems with older adventure games, namely the guess-and-check "click everything on everything" method of playing that's often needed.
My challenge to Tim Schafer, and to any other would-be adventure game developers, is to innovate gameplay. Find something completely new that turns the genre on its side. If you can integrate your story into this innovation, so much the better, but what adventure games don't need right now is new stories tied to old, flawed gameplay models. Jurassic Park: The Game may have been a giant turd, but I have far more respect for Telltale for at least trying something new with it than I do for Double Fine, whose game was a paint-by-numbers recreation of everything adventure games have gotten wrong for decades.
P.S. Thanks