The time one spends in ritualistic practices is wasted; one can spend same time moving forward towards Self-knowledge, which is the main goal.

Isa Upanishads indicates that: By worshiping gods and goddesses and going to the world of gods after death is of no use.  The time one spends in ritualistic practices is wasted; one can spend same time moving forward towards Self-knowledge, which is the main goal. One cannot reach the non-dual destination by glorifying god and goddesses and by doing that, one goes deeper and deeper into darkness. It surely indicates the fact that, the seeker of truth has to drop the worshiping god and goddess in order to get self-knowledge.

It also indicates that, Religious Rituals (Avidya) is Karma (action) and therefore a hindrance.By performing Agnihotra and other sacrifices ([Avidya) is a roundabout way of purifying the mind, and it is also groping in the dark.

In addition, it indicates the karma is limited only to the religious rituals, not on the whole human life. This karma theory based on the human conduct must have been adopted from Buddhism and 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 means that the religion and its  idea of god and goddesses and code of conduct, 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 Bramha Gnana or Atma Gnana.