> Since making a decision in itself is subjective
Not exactly, and that's the whole point. E.g. the whole reason things like credit scores exist is to provide an objective, calculable metric that determines if someone should be offered credit. And, critically, how that metric is generated follows some straightforward rules, so that it can be shown to be free of illegal biases.
Obviously there are other decisions that aren't simply boiled down to a single number, but in general even those decisions that include some subjectivity try to provide clear, objective rationale as to why a decision was taken.