Angels, and demons have "substance" and they are spirit beings.
They have locality and mobility. They move about in the spiritual realm, seeking to influence people (with physical bodies and who can therefore interact with phys. matter.,) whom they seek to deceive.
Quantum physics aside, why wouldn't the Spiritual realm be even more substantial than the physical Universe?
Things (think about what that word means) not seen are eternal, things that are seen are temporal.
Things are distinct.
2 Corinthians 4:18
While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal.
Methinks you have it backwards.
At what point do you stop? Or do you erase all similarities between the Spiritual and the Physical?