In my opinion, the last word, the final word and therefore the most important word, in the Bhagavad-Gita is “morality”.  We can abandon all varieties of religion, but morality is essential.

“Wherever there is Krsna, the master of all mystics, and wherever there is Arjuna, the supreme archer, there will also certainly be opulence, victory, extraordinary power, and morality. That is my opinion.”

Bhagavad-Gita 18.78