There's very few cartoons that really delivered on horror.
Some animators always try to write and draw what they THINK will be scary based on media they've seen before instead of getting creative to make things that can be unsettling in unique ways.
Courage is an example of horror done right, since it uses mixed media and otherworldly characters that feel real but imaginary at the same time. Yes it looks scary, but there's always another layer beneath that makes things feel off.
I don't think the Owl House is going to try to be a scary show, but just a horror themed show like billy and mandy.