Here is the exception to everything said so far. The person who has completely realized the Self — who finds all joy, all satisfaction, all contentment within — has no remaining duty. Nothing more needs to be done. Nothing more needs to be gained.
This is the state of the fully realized sage. It is rare and elevated. For the vast majority of seekers, the path of Karma Yoga remains essential. But Krishna acknowledges that at the summit of spiritual realization, the question of duty dissolves entirely. The sage does not act out of obligation. If they act at all, it flows from a different source altogether.