I think you just want to make a comparison of copyright to slavery.

Property classes are born and die everyday. You can own the rights to publish an arcade video game, but that class of rights would have been way more valuable 45 years ago. NFTs were born and died just recently. You can own digital assets worth real money in an online game that simply shuts down.

Some people may read this and say "these don't qualify as a property class", to which I will remind you that property class used in this way is a brand new term, which I think is invented solely to be able to compare the limitations on human freedom associated with slavery to the limitations on human freedom associated with intellectual property.