A lot of the features you mention sound like old listservs and mailing lists (moderators, archives, searches). And the rest sound like a wordpress blog (archives, tags). It would great to see the perfect combination of all those features in Groups. I barely use them now for how clunky they are.
I feel like Groups wouldn't be an app worth downloading unless you were a heavy user of that feature, which is not most people and therefore a dud by default
I could be wrong, but isn't this what they're trying to do with rooms?
I think (not sure) that I disagree with what he's saying. Groups seems like a product designed to be as easy and obvious to use as possible - all these confounding features would make it harder to use for a large number of people.
It seems like they want something more built-for-purpose - perhaps a mailing list, or even a bulletin board - and I'm not sure Facebook should compromise the usability of their product for a niche use like this.