According to Swami Vivekananda, man is essentially enlightened and is by nature divine. But due to the wrong education and theories, he starts believing that he is a sinner and starts worshiping external matter forgetting the spirituality within.
A man should never forget his true nature – Svadharma.
What is the meaning of Dharma? Dharma means the nature. For eg, Dharma of sugar is to be sweet in nature, Dharma of salt is to be salty in nature. Similarly, the Dharma of a human being is divinity, enlightenment, ability to understand the meaning and purpose of life.
Chapter 4, Text 7 of Bhagvad Gita says that whenever there will be a decline of Dharma in the world, Lord Krishna will manifest himself.
yada yada hi dharmasya
glanir bhavati bharata
tadatmanam srjamy aham
What does the decline of Dharma mean here? Does this mean people will stop following religions, stop believing in God? No, Dharma here means the true nature of human being. Whenever the people will drift away from their inner self, consciousness, Dharma, Lord will appear.
If Dharma would mean being religious, visiting temples, holy places, then the name of Kali yug would have changed to Dharma Yug