evaluating whether something was independently invented, while not necessarily simple, is a more a objective test
Only if you take a very generous interpretation of "independent". For an reinvention to be truly independent, the reinventor would not only need to not have read about the original invention, but also to have not read about anything inspired by the original invention, and not talked to anyone who read about anything inspired by the original invention, etc.
Right, independence isn't binary. There are definitely degrees of dependence. But it's more objective than "obviousness" at least. Obviousness is also non-binary, and because the jury must assess obviousness from a "person holding ordinary skill in the arts", there are additional questions as to what constitutes "ordinary skill" and what constitutes the requisite "art".
Only if you take a very generous interpretation of "independent". For an reinvention to be truly independent, the reinventor would not only need to not have read about the original invention, but also to have not read about anything inspired by the original invention, and not talked to anyone who read about anything inspired by the original invention, etc.