Your understanding is correct, but where your understanding goes astray is thinking that that's a bug. The subjectivity is a feature. It is not possible to specify what should legally happen for all possible circumstances the entirety of humankind faces. Like, literally not possible. We humans can't even create rigorous specifications for what our programs should do that keep up with their evolving requirements, and you want to make life-ruining decisions set in stone based on a rigorous set of predetermined rules about all possible circumstances the entirety of humanity could face any time in the future in an evolving world?
Law is intentionally not code. The world is not something you can program.
Write me the code that says how the Lindsay Clancy case should have come out.
Isn't achieving a rigorous, unique specificarion what civil law tries to achieve? Not that it is a success, but the idea behind it. Sorry if this is a silly question, but this is how I understand it.