I agree. It doesn’t really transition that well with animation. It takes away at the suspense of each panel. The times that Junji Ito is at its best is when you stay on a page and let the moment absorb. His adaptation of No Longer Human is a great read, but I wouldn’t say it would make a good feature film. Animation moves ahead too quickly. Tomie has that same feeling. I’ve never watched the movies they made, but the manga is excellent. Reading it page by page is what I prefer. Devil Man Crybaby was the exact same feeling. The manga felt better.
I like your thoughtful response, even if we don't agree completely. I will concede that there is inherent magic unique to each medium, and the medium of manga (comics, books as well) is that you can absorb the story at your own speed. It's more intimate, more personal, and potentially more scary (since horror is so personal). There's also a greater degree of imagination required, where your mind must fill in the temporal and motion gaps far more than in animation (or film). And as you know your personal imagination if powerful can be more effective to you than anything completely visualized for you from moment to moment. However! That is not to say it will not translate well to film and animation. Cinema can be contemplative, lingering, and dread inducing. Long takes and careful story beats can create tension effectively. The Innocents, Cure, The VVitch etc are classic horror films carried by very still moments and prolonged psychological tension. What film and animation can do that the page can't is movement when such is advantageous and potentially unsettling, or forcing the viewer onward when they are afraid to. Look to Belladonna of Sadness, and Golgo 13, to a time when anime was more experimental, and see the kind of artistic freedom in pace and style you can have in that medium.
The real problem is that with some exceptions, most modern, commercial anime is more product than art, and therefore "moves too quickly". As such it will likely cater to as broad an audience as possible, which means that it won't utilize overly artistic visuals or too slow burn pacing of losing its viewer when ironically, that's what can pull a viewer in. Just look at the trailer for the Netflix one. Why all the camera drifts? Why the flat lighting? Generic drawings? None of that is scary. Anime production pipelines, that's why.