I agree that the authors have failed to create a sense of community by mostly being absent. They do provide a bit of feedback, but it is minimal at best. It is clear that their interest in this project is not aligned with the current interests of the self appointed "user base".
However, in my opinion (and I'm a nobody so you may want to stop reading here), the arc core as well as some of the code that ships with it (news.arc, blog.arc, html.arc) rank amongst the best examples of working lisp code that highlight the power of lisp. news.arc is a great example of the use of macros and arc.arc is a great example of the power of embedded languages (feel free to point out better). To say nothing of the fact that this stuff is simply beautiful in a way I don't get from script-fu, elisp (slime being the one exception), edi weitz libraries, SICP etc. (it probl has something to do with how concise arc is).
So whatever. If more arc is thrown our way, I'll be happy to take it.