But, at least trying to grow said niches didn't hurt. I've been on lemmy for more than a year and i've both created new horror groups and "adopted" abandoned one and, at the very least, now there's some life there. Nothing amazing, but people post and interact now.

If a group you find interesting is abandoned just start posting there, also, if the mods are gone for more than 9 months, just ask to the instances admins to become the new Moderator, all it took is to send a mail most of the time.