Problem definition.
Assuming that humans remain as decision-makers when it comes to defining what problems should be solved, e.g. defining what type of life we want to enjoy, what we would like the world to look like, what makes us happy, etc, humans will need to specify (and most importantly give feedback on) those specific goals, objectives and to keep refining and adapting them to evolving preference frontiers and the evolving human condition.
One could argue that the above constitutes work, and can definitely have both a meaningful and significant impact in the economy.
Note that we call the above "programming" or "machine learning" (~programming from data) in today's world.
Nowhere is written that our goals in life will remain fixed/static. Moreover, inferring (computing) our goals and preferences with varying time horizons and as we evolve over time may be an unsolvable problem and require infinite time and most importantly our feedback.