All rights, human rights included, are just some arbitrary rules some part of humans have decided to follow.
These laws could also set the counter for let's say 5 years after the death of all of the original authors or something like that. There is no reason for these rights to transfer indefinitely.
In many constitutional systems, rights are assumed to exist, and rights are protected by wording that prohibit the government from infringing them.
That's not how patents and copyright work. These are government granted monopolies. The wording goes the other way around: The government is authorized to grant these monopolies. That's very unlike rights to life, property, etc. Patents and copyright don't come from the same tradition as proper human rights. They're different, and there is no human rights argument against limiting them sharply, at least not in the US constitution.
You need to read the US Declaration of Independence.
"We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness."
The signers knew what they were doing was against the Kings laws - but they said, for the first time, there are higher laws that everyone is entitled to. Copyright and patents, while maybe good law, are not among these.
For me the important thing is that _they said_ that there are higher laws. Don't take me wrong, I do like the human rights and all. But they are just a man made construct, there is no higher power bestowing any of them upon us–it is up to humanity to ensure that we keep them.
These laws could also set the counter for let's say 5 years after the death of all of the original authors or something like that. There is no reason for these rights to transfer indefinitely.