> All "property" is imaginary.
When it comes to the current legal notion of property, then yes, assigning something as someone's "property" is imaginary.
The problem is "real" property cannot be duplicated without expending resources, whereas IP can be duplicated for free. For example:
If I make a car, you can't just "copy" it. Taking the car is stealing, and I think that is immoral because you have deprived the original owner of their work.
If I make a short story, then "copying" the story means using your own pen and paper (or your own hard drive to place a sequence of bits) to copy. I don't think this should be illegal. That is, I don't think that having a particular sequence of bits on your hard drive should legally allow men with guns to enter your home, label you a criminal, fine you, and/or send you to jail.
In that sense, not all property is "imaginary." We can make a distinction between tangible property, that exists as mass, and intellectual property, which is a set of ideas/words/code/etc. Tangible property is rivalrous; we can't both use it at the same time. Intellectual property can be used by many individuals at once, so calling it someone's "property" and enforcing that claim with force creates artificial scarcity.
I do feel bad that people who expect and rely on IP laws could feel cheated if IP laws were to disappear tomorrow. But to pretend IP law is some sort of natural thing is a bit naive. People have been creating ideas since we evolved a brain. People will continue to create without IP law. To make money off of your creations just requires a different business model.