Well this particular example is only popular thus far within a very niche, but very passionate audience, is getting only a limited theatrical release where I anticipate it will be very divisive and not be particularly profitable given the extremely limited amount of screens, and then go off to the modern equivalent of "the rental market and cheaply licensed titles on television" which is niche streaming services that cater to limited audiences.

Contrast this to something like, say, The Blair Witch Project, a film which got heavy festival buzz, had a successful limited theatrical engagement before going on to a very profitable wide release, spawned an entire franchise, and is still considered by most reasonable measures to be a considered a Cult Classic.

Please, let me clarify I'm not saying that "Skinamarink" is a Stone-Cold Cult Classic at this time. I was offering, as a rebuttal to OP's assertion regarding cult films, a modern film that, in my experience, is showing all the hallmarks of something that has a strong chance to, WITH THE PASSAGE OF TIME, develop that reputation.

Interestingly, people keep saying "usually", "generally", "almost all" with regards to the criteria of what constitutes a cult film which is literally admitting there are cult films that do not fulfill said criteria. Again, my main point is that films like these are still being and will continue to be made.