Community building involves more than just posting. It’s “If you post it, post about it everywhere else, and talk about it with everybody who will listen”. And then dealing with months if silence while you keep posting things that inspire others to join in.
Forums used to be lively and self-sustaining with memberships in the low hundreds. You only need “mass adoption” if you want and unending stream of novelty bullshit that you don’t actially want to engage with to entertain yourself with while on the toilet.