God takes it seriously enough.
Jesus certainly kept busy dealing with demons that you claim aren’t real.
Unless you are claiming that He was wrong or that you know more than Him.
Is God lying in Scripture about the demonic and the devil?
I always consider the historical context in which things happened or were uttered.
Jesus was speaking to a certain people, in a certain time - many of whom had little intellectual development and were influenced by lots of traditional superstition and symbolism.
The Devil - or ‘demons’- may have been useful designations for Evil, back then. But that doesn’t mean that modern people should personify and fear those same things, in the same way.
I believe that Individuals should stand up and take personal responsibility for their own minds and imaginations. What you believe in CAN hurt you; what you don’t, Cannot. And I don’t like any religious system that teaches people FEAR. Jesus, to me, seemed to be all about telling people to adamantly reject FEAR.
(I don’t think that Matthew 8:13 refers only to faith or belief in the Positive. I believe that the Law is simply that ‘it is done unto us’ AS we believe, either way.)
And I don’t take everything in the Bible absolutely literally. I doubt that you do, either.