I'm not sure what your issue is exactly. Is it about him as a writer and his 'obligations', or are you approaching it as a frustrated fan who just wants the next book? Both? If it's the former, then I can kinda understand, and sometimes I don't like the romanticising that's done with writers (writers block, the muse etc.)
HOWEVER, when someone buys your book, that's their decision. The thing about entertainment, is that's it's a market measured by objectivity (sales) but is reliant upon subjectivity (people).
The issue I find with your argument, is that you're applying the rules you might to someone like a doctor/teacher, who has an obligation to perform to a certain degree because it's part of the agreement they've made. There's a reason you need qualifications for those jobs. As an author, you can write whatever you want, and there is no hard-set skills beyond basic grammar required. Clearly, you don't need to write a super thought-provoking story in order to be successful, you don't need talent either. Unlike a teacher/doctor who have to follow a certain curriculum/rules and are expected to be up to a certain standard based on the regulations we have in place. You cannot classify yourself as a Doctor if you're not qualified as such. But if a writer doesn't release a book when expected, there's nothing wrong with that, because there's never been any regulations/rules to suggest it's an issue (unless stated otherwise in a contract). It might be frustrating, but the writer never agreed to such a thing, even if they made promises themselves, there's no rules to enforce punishments on them for not fulfilling it, so there's no issue.
An author has a contract, but that's not between them and the reader, it's with their publisher. The publisher can make demand so long as it fits the terms agreed to, but there's no such agreement with the audience, besides the imaginary one readers conjure up in their heads.
Now OTOH, if you're complaining as a fan, then I'd say the same thing as before. Whenever I hear this talk about 'books taking long', I just wonder why people don't just read other books and get over it, or better yet, make their own if they're up to it. I get the initial annoyance, but it's been a while now. The same thing with Patrick Rothfuss, I know it's taking ages, but people seriously devote hours of their life if not longer to complaining about something so trivial, whilst they could be spending the time reading someone else and find something perhaps even better than the series they're waiting on.
