Consider these (rhetorical, I am not sure I'm up for the nuanced debate given IANAL) questions:
1. Who owns the rights to a commissioned piece of art? The artist, or the commissioner? Which rights?
2. What about derived works of art made with or without the permission of the original artist(s)? When a book is turned into a film, who "rightfully" owns what? When the Rolling Stones wrote Sympathy For the Devil, did the estate of Mikhail Bulgakov have a right to feel aggrieved, and should they have received royalties?
3. What rights can be assigned/transferred, and what rights can't be? What needs to happen for that process to be legally binding?
4. Is a monkey capable of being a willing participant in a photograph, or a contract assigning rights in any way?
5. Same question, but for a machine? What does it mean for an AI to assign rights, or assert moral rights?
5. If the law makes it clear that a legal party to a statute (law), or contract must be a human or other legal subject (an incorporated business), can those laws and contracts lawfully apply to an animal or machine?
6. What is the intent of intellectual property law? Many argue it is mostly civil law, that follows the spirit of civil law in striving towards fairness?
We can argue if intellectual property law implementation is just, but your issue seems to be that the time invested in planning a creative act is the central tenet on which a copyright protection should be determined.
If so, Picasso was wrong to argue that his quick sketch on a napkin took him "a lifetime" to create, and your argument is just and correct. I disagree.
Regardless, what do you think the law is attempting to actually protect which is not "time taken to plan and create the work"?
Note when thinking about these questions it might be helpful to remember that ownership, copyright and moral rights are not all equivalent things in law.