From the article:

    Diminishing marginal returns:– some tasks performed by
    doctors have more impact than others. If there were one
    fewer doctor, the highest impact tasks they perform would
    be given to someone else, so the total impact wouldn’t
    reduce proportionally with the number of doctors.

In other words, that operation probably did add decades to this man's life, but this is the kind of critical care that we would find someone else to do if this doctor hadn't been there to do.

The question is, if you're considering becoming a doctor, what's the potential benefit that's due to your choices? How much good do you do that wouldn't have happened anyway?