I feel like most users have switched back to Reddit, but I’d like to have an alternative to Reddit.
I might post memes here but I don’t want to keep this active by myself.
This is also a common issue within lemmy, and I did try to revive 2 other communities, but one barely succeded while the other just didn’t see much new posts.
The larger slice of life community was completely dead in my absence as well, and is recently active again since I started posting again. Because it aggregates content from smaller more specific communities, regular activity resumes much quicker.
As for the amount of people needed for an active community, I think 500 is quite an optimistic estimation. I estimate less than 1% of subscribers ever post anything. If I quickly take an example, the Lucky Star subreddit has 12k subs and seems to have on average a few posts a day. A few thousand subs seems to be needed for regular activity.
I run a small discord server which has about 200 ppl and it’s fairly active (few messages per day), but that’s a different format/platform
As for getting new members on here, try asking the mods of those communities for a collab or affiliation or something