It's taking your experiences and inspirations and making a new product out of it. Gravity Falls combines a lot of elements from Hirsch's childhood (Him and his sister, other family members, tourist traps he used to visit) as well as things like Simpsons, Twin Peaks, and X-Files. GF isn't "original" so much as it is fresh. It's like how Adventure Time was fresh up until everyone started copying it.
So far, all we know from Owl House is that it combines all of Dana's favorite characters from other existing works while also visually looking like art from previous animation jobs. And considering she's riding in on the GF train, her show visually looking like GF is just enforcing the staleness from this type of art and design. It doesn't even look like it's own thing, it really does look like you could throw Bill Cipher in there and call it a deleted scene from Weirdmageddon and everyone would believe it.
If you compare it to the sister show Amphibia, you can at least tell it combines a lot of Matt Braly's interest in frogs, enough that he can draw a lot of cool character designs out of it. If he was going to go the, "I will steal what I like" route, the girl would've fallen into a Sonic the Hedgehog-esque world (His favorite video game character) and would've befriended a colorful porcupine whose best friends with a flying cat or something.