Furthermore, I have a simple question to pose.
Did arne put a copyright on his palette when he created it?
In most countries, in most situations, copyright is automatic. Formally 'copyrighting' something is really about establishing a stronger standard of proof that you created the artefact you are claiming copyright to.
the artist who sees that his work has created inspiration, should be humble enough not to demand acknowledgement.
Why *should* they be humble enough not to demand acknowledgement? Acknowledgement is generally a social good, not only for the source but the user, and it's their choice what terms creators release their work under; the morality of that choice is contextual like most things, not universal.
The only situation in which crediting your sources would reasonably be considered onerous is if you have dozens of them (this is very unusual, for a single artwork)
It seems to me you are arguing that you should be allowed to behave irresponsibly with other people's creations (as opposed to what you seem to think that you are arguing for, which in my observation is, to do your own thing and create your own art without being harrassed about sources and crediting. Which is a very ordinary thing and happens on pixelation constantly,)