I think public gateways are great, and we should have more beautiful/polished ones.
But I also think that they should be strictly opt-in, as they are now.
In fact the opt-out that you, @entron, describe used to be the default and it was intentionally changed to an opt-in.

If you want more than "this is how it was decided" though, here's what I have to offer: I think the mistake you're making is equating growth in number of users with success. Currently, ssb "kinda works" and yes, we could use many more devs. But ssb is not just a protocol/technology; it is also a community and a culture. "Growth-hacking" our way into the mainstream might actually kill the project dead, simply because what is currently implemented is not built/able to deal with the issues that come with that. Think moderation, regulation, censorship, ...
One rule of thumb a friend used for this is "Growth at the rate of trust." We need to build ssb to serve those that currently use it. Our resources are constrained enough for that. We really shouldn't be spending our (spare & rare) time on things that would only attract & serve people who are (currently) perfectly fine with how facebook & twitter work. They'll come around sooner or later, we don't need to be aggressive about it.

That being said I also think/hope that ssb will one day serve billions, and it would be amazing to have a static-site kind of viewer. Technologically very cool and given the size of the dataset probably hostable on a pi zero? 😀

Do you mind sharing a bit how you're going about it? Language, framework, design-wise? When new messages come in, do you re-generate the whole thing, or can you identify the thread/profile/channel pages that need updating?