I wouldn’t necessarily count all of these as reasons to throw out your idea though. For feature creep, wouldn’t cutting scope back to the core features be enough? Likewise, if you don’t place a high enough value on design, that isn’t really a problem with one’s idea as much as it is a problem with one’s mindset.
Aside from those, I think all the other sections were on point. Personally, I just went through the “Purpose is Vague” situation. We had a clear purpose down to a sentence, but due to a variety of factors our belief in it fizzled over time and we decided to move on. Planning to write more about that soon. Thanks for the article Moses, I enjoyed reading it!