It is true that land is not obtained by labor, but it is still a limited resource needed for production, so if someone owns it, that someone will most of the time only agree other people use it in exchange for part of the final product.
in exchange for part of the final product.
If that final product is 'money' then I understand your logic and also why this comic exists. At the most minimalist interpretation that inherent rentierism is an example of an unnecessary extraction of the value of labor from those who produce it.
But again, this is about wages. You can't slide between 'wage earners' and 'owners' any more than you can define 'land' and 'landowners' interchangeably.