To Arjuna, wondering why renunciation of work ( which is what he thinks he is doing by refusing to fight) is treated Krishna on par with performance of work (which Arjuna considers as inferior), Krishna gives a categorical answer in the key second shloka of Canto V : 'Renunciation and activity both liberate, but to work is better than to renounce.'
No question of it -- the Gita is the gospel of action, selfless action, fruit-forsaking action.
Gracefully, almost unobtrusively, Krishna brings in here the Upanishadic concepts of the Witness and the Participant. Two birds sit on the golden bough of the pippala tree, says the Shvetashavatara Upanishad. One bird eats the sweet fruit, the other watches the first bird eat. Both are happy. One is happier. Which ? And why ?
Our body is the sweet, sensual pippala tree. The atman is the watching bird. Our deeds are the eating bird. The watching stops when the tree withers and dies, and the watching bird flies away. Till that time, eating and watching proceed simultaenously. So the advice of Krishna is simple. Watch life detachedly. Enjoy it coolly. Savour your deeds as you would the performance of an actor in a play. Be involved - and yet free. As he says in shlokas 8 and 9 : 'Seeing, listening, eating, talking, breathing .... he should say, "I do nothing at all, only my senses are busy."'