Standalone forums - especially niche forums - are going to be harder and harder to grow. Communities these days are build on (or with the help of) social platforms. Dismissing Facebook, Twitch or Discord just because anyone can manage a page, a channel or a server is a mistake imo.
As far as I know what matters to build a successful community is reach and engagement. Scaling your reach via this forum alone is gonna be tough af imo. Usually this is done by combining marketing campaigns, social medias and a solid ecosystem of partners. As for engagement it's all about content. AN is a forum, it's also a news feed, it could be a white label shop, a video feed, some sort of occasional live stream...
That said, my take isn't worth much as I have no idea where you wanna go with this website from here on :))