Whether something is popular or mainstream enough to be spoken of often, or niche enough to rarely or never be talked of, seems irrelevant to the topic at hand.
Personally I think it is an interesting looking outliner for someone needing something online, and I’m glad to have learned of it.
I agree it is irrelevant, but I am surprised it has never came up in drmajorbob’s experience.
Dynalist is useful, for me, for everyday use, notes, to-do’s, sync et al.
I think it is not to be compared to Scrivener.