Even TV shows that have been off air for a decade often have a thriving community. Merlin, the BBC show, has several posts per day. Similarly with Smallville. Lemmy’s communities are smaller and tend to be broken up across instances.
I feel like there needs to be instance aggregation for Lemmy to really work in the long run (and really this is probably true of the fediverse in general). Having to add communities across multiple instances, and not being able to browse them in a centralized way, really detracts from the experience. On Reddit, I subbed to the stuff I wanted and just lived off that feed. With Lemmy, I feel like I have to stay in unfiltered view to get anything of interest–the fragmented niche communities are just too limiting.
Reddit will have active subs for specific board games. The general board games magazine on Lemmy has 1 post a month.
So ya, if I want to read comments on the latest episode of Loki to see what things people picked up on that I missed Reddit is currently the only place to find that.