Yeah, I get the same thing as you. What I've done so far is I made a few communities here and am trying to fairly reliability populate them with content. Some of those communities are niche and I feel like I'm posting into the void sometimes, but occasionally I've gotten someone else actually posting some content in them. It does definitely take some commitment to bootstrap a new community, as people just won't start posting on their own there until there's a critical mass. So you just gotta take the hit, post into the void a while, slowly increase that subscribe count, until finally others start to join in.
It's easiest with communities focused around memes or links, but I think it'll take more effort with more niche hobby or technical communities, e.g., for programming languages or niche hobbies.