Mm... you do have a point, but I would argue that the content is generally better at the very least to the degree that it's actual people sincerely posting things rather than bots, shills and karma farmers spamming and/or astroturfing.
And yes - niche communities are extremely underpopulated here.
I don't think the solution to that though is to aim for more generic "content" with the hope that it'll lead to broad growth and that a byproduct of that will be to bring more people who happen to share your interests. The solution IMO is to get on the communities you want to see grow and start contributing stuff, right now. Even if you're just posting to one person, keep at it, and pretty soon it'll be two, then three, then...