TL;DR
We should be encouraging individuals to push for their proposals and reach out to more people outside of the current Stack Exchange demographics, so the Q&A community grows bigger, instead of just ignorantly criticizing their endeavors. Don't get me wrong, I don't mean ignorance as an 'ad hominem' offense, we can all be ignorant on some subjects even if very proficient on some others.
Although I consider myself a person who knows a lot of things, one of which is programming and also making money out of that, but let's keep it simple and say...
I'm a programmer... but I'd love there to be a site to make questions about health, a site for that very purpose, but I wouldn't want to ask in a site where doctors are talking in higher abstractions of medicine research, I'd be totally confused and rejected by the community for being out of place or "off topic".
If you are a programmer and can't tell the difference of medicine and health vs medical practice & researh, or cognitive studies vs psychology practice, that's ok but you shouldn't suggest decisions to be made based on ignorance. For example suggestions of merging sites and complains about duplicates. I see plentiful of such rushed suggestions that display ignorance, maybe I've even make a couple mistakes of those.
If we are not going to help, lets at least not be an obstacle.
Many doctors can't tell the difference of server vs web apps (a few do), and even if you are a cryptographer some people may ask you to fix their computer... most programmers get upset or at least a bit offended when that happens, for good reason.
I think you see the point now.
I don't think the problem is so much the different proposals. A few are more fragmented than they should, sure... but the ones you are pointing out are not, I think starting with an overly broad scope could actually hurt a site more than it could help.
The real challenge (not problem) -IMHO-, is the fact that StackExchange was born from a Programmers' culture and Computer Sciences.
Observe, most of the successful SE communities are either:
- Closely related in some way to IT
Example: StackOverflow, Programmers, Server Fault, etc.
- Benefit from the use of a computer on a daily basis (or at least weekly basis)
Example: Theoretical Math, Physics.
- Even Videogames (Arcade) are computers (modified to fit a single purpose).
...the communities are different and so are the questions, the same should apply to Health and other sciences, people are just having a hard time circumventing that inertia and acting accordingly.
I find it short sighted to try and force all different aspects of other sciences and fields of knowledge to be in just one single site for each.
My advice for all people trying to start new SE sites would be:
There are way too many "computer people" in here, we need more diversity!
Go out there and talk about your new proposal to your colleagues!!!!