If, as a physicist, you develop a system of turbulent thermal insulation and its theory this may not be so important if inertial confinement fusion is chosen for power reactors.
As a teacher, what you accomplish is a function of how bright your students are and how hard they work.
A computer scientist who develops analog or hybrid computers may be made obsolete by the progress in digital machines.
As an inventor, the creation of the tandem mirror or tandem cusp may not be very significant if closed magnetic fusion systems are chosen. Similarly, a magnetic hairpin limiter for a Tokamak may be obsolete if we use laser fusion systems.
A philosopher who has spent his time developing a theory of value pluralism will have wasted his time if value monism proves to be correct.
An engineer may have an easier time judging his success and the value of his work.
An aerospace engineer will know if his rocket climbs into space.
A software engineer will know if his control software keeps the plant working within the desired parameter range.
As a vacuum engineer I know over what range of vacuum pressures my chamber operates.
(But, of course, an engineer's product may be of uncertain reliability, safety, and cost and people may not want it. You can design an aircraft but a competitor's product may get the contracts. Your software may be subject to security risks or crash frequently. A cheaper substitute may be available.)