Quite the opposite. If skills are infinitely transferrable, then the skill level of a developer is a function of time they have spent in the field. This makes

Quite the opposite. If skills are infinitely transferrable, then the skill level of a developer is a function of time they have spent in the field. This makes a senior developer extremely valuable because they will always be more qualified for any job than someone more junior than them and there is a limited (and shrinking) number of people who are at their skill level or higher. (to be clear, I don't believe that skills are infinitely transferrable)