No, there is no such newsgroup.
On the other hand, no one prevents you from starting one. On the
contrary you will get a lot of support as an increasing number has
complaining about the sad situation.
Suggestion. Go for a group moderated by filtering out all crossposts:
most of the garbage is crossposted and most of the articles that are
posted to s.c.jewish only are relevant to the group.
Added bonus: it is trivial to make the filtering automatically.
And the key point: no one will accuse you of censoring, as you
criterium of choice is based on the form of a message and not its
Afraid I don't have the time or energy to do that.
Maybe there is a mailing list of some kind? If I can find one, I will
post it here.