We're not talking about users, we're talking about attackers and developers. Why would users have anything to do with our discussion?

Plenty of cryptography is also designed by individuals not in the service of any nation state (as far as we know, anyway). In fact, some argue that such encryption is more trustworthy than encryption developed by nation states themselves.

Developed by academics, but tested by both academics and the government. The testing is the thing that's actually important.

I can't speak for any and all activists. It's really up to them to acquire such expertise or get advice from people who have such expertise.

The point is that the technical expertise is not available. It's not up to them. It's not available. What you suggest they do is not possible.

That said, the problem here is no different from figuring out which encryption to use. So your criticism applies equally to encryption as it does to steganography.

Nope. Get back to me when we get government backed standards and recommendations for anonymity (hint: we have them for crypto).