If you care about American politics and being outraged at every and any thing thrown at you during the day, it is active enough. However you are SOL if are curious about any other topic that does not involve narcissistically talking about yourself.
Assuming you are invested enough to find or create a community for a topic you care about, be prepared to be talking to yourself for a long time and consider yourself lucky if you manage to get 2 other people commenting on it.
Congratulations. You are bringing your dozen communities that only survive due to your incessant work, which kind of exemplifies my point: Lemmy has maybe a handful of communities outside of the politics/meta-fediverse topics.
How active is Lemmy now?
How many millions of users does it have? How many posts? How active are they?