And yeah, I get what you are saying, I'm using it the same way you envision snikket, just for my wife and I. Considering how much time I spent on the initial setup, I can very much see wanting a preconfigured version.
I guess the site was just too "non technical" and went over my head when I tried to grok it (before, a while ago, and now before writing the comment), the lack of a download option for the client on the snikket site combined with repeatably talking about invites just rubbed me wrong.
As I have already setup my server, and have gajim/conversations (which afaik are the best modern Windows/Android clients, for Windows probably even the only one storing modern xmpp) for desktop/mobile, I have no need for snikket, but my view now went from negative to very positive ;)
I'm still experimenting with the messaging on the Snikket website. However my general approach with the site was to pitch Snikket to people who don't know what XMPP is, which is, frankly, the majority of people. Instead, I wanted to focus on explaining features it enables rather than protocol details. But I'm aware it has caused a lot of head-scratching among people who already know Snikket uses XMPP :)
I see Snikket as kind of a gateway into the XMPP ecosystem for people who are unfamiliar with it. After all, if you're already familiar with XMPP then the chances are you'll probably be happier with Prosody or ejabberd, and you'll already have opinions about which clients you want to use (e.g. the upstreams of Snikket).
Snikket seems to just be a focus or lens on Prosody that answers that question for the mission statement you gave.