With all respect to Matheson — and he deserves enormous respect — I’m not sure how much this applies to superhero comics (or adaptations thereof), which are usually stuffed full to bursting with virtually nothing but fantastic elements.Richard Matheson would disagree. His philosophy was that if you want to include a fantastic element in a story, it's important to keep everything around it as grounded and believable as possible to facilitate suspension of disbelief.
But I mean, if the cube Earth didn’t work for you, then it didn’t work for you. No harm no foul.