An objective decision is one that is independent of the decision-maker, as long as that person knows what they are doing.
A subjective decision is one that is dependent on the decision maker.
In my experience, engineers (and possibly other humans too) tend to love an objective decision-making process. Objectivity seems to remove fallibility.
An objective-sounding way of making a decision is to carry out a multi-criteria analysis, in which the different factors are objectively assessed and then the different factors are given a weighting. The best answer then drops out of the process.
But even if the assessment of different factors is objective, the establishing of the weighting is subjective. Our objective process has become subjective.
That is fine, as long as we have the skills for making a subjective decision. Subjective decisions take time, require the application of judgement, draw on experience and values. These are factors that are not easily short cut.