Deeper-self-search reveals the fact that, the karma theory is meant for those who are immersed in worldly life thinking the individual life within the particle world as reality. In path of truth the karma theory becomes a great obstacle in realizing the truth.
When Sri, Sankara says clearly, the universe is not real. He says that Brahman and Atman are one. The ultimate and the Absolute Truth is the Self, which is one though appearing as many in different individuals. The individual has no reality. Only the Self is Real; the rest, mental and physical are but passing appearances, then it indicates the form (waking/duality/mind) is unreal the formless is real (soul/spirit/self/FW). Therefore, only Atman is real because there is no second thing other than Atman.
He also clearly mentions that:-
The path of religion, theory of karma, path of yoga and the path of wisdom were intended for different classes of people. The wisdom is for the advanced seekers of truth. It deals with the nature of the ultimate Truth and Reality. It is meant for superior aspirants who have inner urge to know the truth and it is not for those who are immersed in earthly desires.
Sage Sri Gaudapada says: - The merciful Veda teaches karma and Upasana to people of lower and middling intellect, while Jnana is taught to those of higher intellect.
It means the people who follow religion and worship of guru and conceptual god and believe in karma theory are lower and middling intellect. But in this modern world people are sharp enough to understand and assimilate ultimate truth or Brahman or god. Thus it is high time to discard the lower knowledge and move ahead to realize the ultimate truth, which is Brahman or God.
They alone in this world are endowed with the highest wisdom who are firm in their conviction of the sameness and birthlessness of Ataman. The ordinary man does not understand their way. (Chapter IV — Alatasanti Prakarana 95-P-188 in Upanishads by Nikilanada)
This karma theory based on the human conduct must have been adopted from Buddhism and also other theories based on human conducts.
When it says: Perform the obligatory karmas without any attachment to the fruits, and at the same time worship gods and goddesses, again without any desire to go to heaven - then you can get the benefit of both, liberation and bliss. For those who are not yet ready to renounce, this path is recommended, it mean that the religion and its idea of god and goddesses and code of conducts, and its rituals are meant for the mass who are incapable of thinking of the beyond.
In addition, it also speaks of heaven the abode of gods, where one goes after death, and it speaks of rebirth, this contradiction, seeker has to conclude that religion, rituals god and its code of conducts are meant for the mass that is not receptive to self-knowledge or Brahma Gnana or Atma Gnana.
When the self is not the body (‘ego or waking entity’) whatever one sees, knows, believes, experiences and feels on the base of the body (‘ego or waking entity’ as self is bound to be illusion. Thus, the karma performed in illusion is bound to be illusion. The birth, life and death is happening within the illusion, therefore it is bound to be illusion. Thus, rebirth and reincarnation theories based on the false self within the false experience are bound to be illusion on the base of the true self. Only the witness of the illusion is real (Brahman). Therefore, everything has to be viewed and judged, on the base of the Formless Witness (soul or consciousness) in order to overcome the illusion/duality.
The seeker of truth has to know somewhere he is going wrong, and it is for the seeker to go on his own and remove the obstacle. The greatest hindrance is mixing religion, god, scriptures, and yogic theories. Moreover, attachment to scriptures, personal god and religious code of conduct keeps one permanently in the grip of duality.