lemmyverse.net/communities lets you sort results by subscribers, active users, number of posts etc so you can look at the metric you're most interested in :)
I prefer looking at c/all/new for interesting posts. If I see enough from a community, I subscribe. The is no reason to participate in an inactive community.
The thing is, if everyone just goes to the most active instance, we end up with another centralized community, and it kind of defeats the purpose of the whole thing imo.
By community I don’t mean the instance. Should have been clearer that by community I mean „subreddits“.
One subreddit could be popular on instance X and another one on instance Y. So what I want are the most popular communities of all the federated instances.