But there IS audience goodwill, among the actual backers. That's what you're ignoring. There's just not really any evidence that backers feel burned by this project in any big numbers, and it's not really DF's fault that misreporting of the story has made the situation sound a lot worse than it is. Backers largely don't feel 'bitten,' at all. Feedback on Act 1 wasn't spotless, but it was very good.
Also, no, the engine that Broken Age is made in is, in fact, DRASTICALLY more sophisticated than what is possible in AGS, and also having developed the tools has already enabled them to develop other 2D games.
And it's extremely, extremely naive to compare what one studio did with their project to another. There are too many variables. Besides, even if you do compare them inXile's record is nowhere near as spotless as you suggest. Wasteland 2 was delayed by around a year, and required additional publisher funding from Deep Silver. Did you forget that? So let's not pretend it was some incredibly smooth project in comparison. Broken Age, meanwhile, has managed to reach the end of development without publisher involvement (only a distribution deal)
What happened with Broken Age is nothing unusual, development wise. What's unusual is how much scrutiny the game came under, and how successfully DF managed to obtain extra funds without resorting to publishers.
As a backer I got to say do do feel ,not burned, but just disappointed that Double Fine's recurring problem of cost overruns, and projects ballooning in scoop were not publishers in the end because of publishers but simply because Double Fine is bad about underestimating costs and letting project scope increase beyond the teams grasp. All those things I tried to blame on publishers in previous DF games in the end where mostly DF problems and not those of publishers. I am going through the same thing with Oblivion and the mass of bugs that I have been encountering in Pillars of Eternity.
Mind you I love both these games I am weary of kickstarting another project from either company unless it really hits something I am dieing for. I gave both of them a chance to shine without a publisher and what I got was the same quality of game I would have gotten from them under a publisher in a sub-genera that no publisher would have touched. It is honestly what I should have expected but Publishers as short sighted and evil 100% of the time has been thrown around by gamers so much that that brain bug got me to. Though I am more weary of Double Fine after Spacebace DF-9 as while not kickstarted it showed that DF both is willing and simply doesn't have pockets deep enough to finish a game if their reach exceeds their grasp.
I'm still going to keep buying double fine games but super, ultra pre orders for support and then hoping I like what comes out at the end is something I am not going to do again. DF publishes some great games and continues to do so but I will support them by buying finished games. Then again I have sworn off early access and kickstarter for games along with my never preordering a game so not like it is just Double Fine I am focusing on with that.