The fact that Pennywise is a supernatural creature doesn’t even need to enter into the equation, as everything that makes Pennywise terrifying in the new film can be linked to that erratic madness.
The madness of Pennywise is also clear on the screen.
The previous version of Pennywise adapted for the screen was a more cold and calculated evil.
You never know what the creature is going to do, only that you won’t be able to guess what it is.