We've done this one before. The answers haven't changed.
(1) Yer average punter can just about cope with the web and email but really doesn't want to be bothered with finding out what newsgroups are and how to configure a newsreader. Sure you can use a web interface like Google ... if you don't mind a six hour delay until posts become visible. "Fast?" - not.
(2) If you want to use existing newsgroups, then feel free - just go and do it. If you want a new set of PPRuNe branded newsgroups then how many years do you think it takes to propogate them to all the current users' ISPs? OK, so that's easily solved - set up a private news server and it can carry any groups you want. But of course that costs hardware and bandwidth, so not free, plus even harder for the non-techie punter to set up.
(3) It is not true that newsgroups cannot be moderated. There are plenty of public moderated groups - search for groups with "moderated" in their names. You can set up private groups on your own server to be moderated. You can require authentication on your own server, so you can track who's posting. Spambots that try to post to a private server with authentication switched on (does this ever happen??) will fail. If you have a private server which doesn't propogate anywhere you can even delete posts after they've appeared.
(4) Putting advertisements into every post in a newsgroup is really really irritating. So, no adverts. So, no advertising income to pay for the service, so we all have to chip in even more.
Everybody still with me? - if not, then that proves point (1).
I'm afraid that next time this is suggested the answers will still be the same.
(Running a parallel news server to serve up the contents of the forums via NNTP might be helpful as it would reduce bandwidth ... except that the service isn't bandwidth limited. And you'd somehow have to advertise this to users in such a way that advertisers never discovered its existence.)