The slow pace isn't for everyone, but in my opinion, it wouldn't have worked if it was any shorter. I disagree with the suggestion that it should be condensed down. Being a child terrified at night is not a bunch of quick scares with normal movie-like pacing. It's agonizingly slow, trapped the surreal environment that is your home at night, unable to do anything but wait out the long hours until the day comes. Since the windows are removed, the night is literally endless for the children in skinamarink. Normal movie pacing would take away from the hopelessness and dread of their situation.
If I had one criticism, it would be about how horrible it is to watch children get tortured endlessly. I'm not a fan of horror movies that disturb me in the not-fun way, or horror movies that have torture. It was a bit much for me.
The scares weren't the normal cheap jumpscares, they were genuinely horrifying & paralyzing. I still get chills thinking about the phone-eyes one. The movie was surreal and disturbing without going totally overboard, and I am a changed woman after watching this. Highly recommend.