My Reply: Varnaśrama Dharma is not fully viable in this modern age, Kali-yuga. The only completely viable dharma in this yuga is hari-nāma-saṅkīrtana. (“harer nāma harer nāma harer nāmaiva kevalam, kalau nastyeva nastyeva nastyeva gatir anyataḥ”).
That said, Varnāśrama Dharma is still partially viable – and the general principles are still useful and valid. The Gita’s concept of Varnāśrama Dharma is not a janma (birthright) system at all, it is a guṇa-karma system (“catur-varnyam mayā śṛṣtāṁ guṇa-karma-vibhāgasa”) – a system based on your actual character and deeds. You are born into a brahmin family, but that does not mean that you have brahmin dharma, it means that it might be relatively easier for you to adopt brahminical occupations and character traits. But until and unless you adopt the deeds and character of a brahmana you are not a brahmana, instead you are “brahma-bandhu” (the relative of a brahmana). Of course, the caste system has degraded so extensively that most likely a person born into a so-called brahmin family today could often be brahma-bandhu-bandhu-bandhu-bandhu (the relative of a relative of a relative of a relative of a brahmana).
In kali-yuga, Varṇāśrama Dharma is not primary, it is secondary. Hari Kīrtana is primary. As a secondary dharma, the specific exact details and strictures of Varṇāśrama are not important, it is mainly the essential concepts and fundamentals of the system that are still reasonably viable today. Perhaps in the future things could possibly change for a few centuries or so, enabling Varṇāśrama to be a little more viable than it currently is. Currently the only useful thing is to recognize ones character and deeds as being most akin to either intellectual, administrative, mercantile, or artisan. And based on that, cultivate a few essential qualities intrinsic to each category. For example one with a primary intellectual bent needs to cultivate simplicity and honesty. One with a primary administrative bent needs to cultivate political knowledge and respect for intellectuals. One with a primary mercantile bent needs to cultivate the knowledge related to their field and the giving of ample charity, and one with an artisan bent needs simply cultivate their art/technical field along with the quality of helpfulness when called upon.
Krishna’s advice here in the 3rd Chapter of Gītā is translated to modern terms with more integrity when we use the word “responsibilities” rather than “duties” especially if by duties we begin thinking of some particular social structure like the caste system or some semi-workable concept of Varṇāśrama Dharma. He is advising Arjuna, “you have your responsibilities. Stick to them. Sticking to your responsibilities is always noble and pure and will always uplift your character and your life. Even when your responsibilities seem to be hard, or seem to be debased and difficult – stick to them at all costs.”
— Vraja Kishor das