It doesn't matter what 'the developed world thinks'.
For someone who wanted access to a Green Card, to have to give it up is fairly substantial.
And FYI anyone in the developed world, were they to know what a 'Green Card' actually was, would find it probably invaluable. The optionality that comes along with being able to move freely and work in the US is a big deal even if it's not apparent at the start of one's career.
The parent comment was responding to the grandparent comment's apparent claim that a green card is equivalent to the whole developed world. There's no dispute that a green card is valuable.
A more useful correction to the parent comment: GP probably just meant that the green card was what currently gave them access to the whole of the developed world, not that it's the only way to access some of the countries in it.
A US green card doesn't give you 'access to the whole of the developed world' though, it's meaningless outside of America.
France's customs for example don't care whether you have a US green card or not, it makes no difference in whether or for you're allowed to stay in France.
For someone who wanted access to a Green Card, to have to give it up is fairly substantial.
And FYI anyone in the developed world, were they to know what a 'Green Card' actually was, would find it probably invaluable. The optionality that comes along with being able to move freely and work in the US is a big deal even if it's not apparent at the start of one's career.