Lemmy not catching on and Reddit dying aren’t mutually exclusive, unfortunately. I personally know quite many users who left Reddit, but never made the jump over to Lemmy, because they mostly stayed on Reddit due to particular communities. With those communities getting decimated during the APIcalypse and its fallout, they had little incentive to join Lemmy.

Ultimately my personal opinion is that Lemmy is going to persist, even if it doesn’t cross certain thresholds, it is still a part of the larger Fediverse and due to its interoperability, Lemmy can benefit from the success of the Fediverse, even when not being all that successful by itself.