The Vedic Gods are mainly Fire, Water & Wind. The prayers offered to them are for health, wealth, progeny & annihilation of enemies, which are hardly spiritual in nature.
Some of the actions of the "Incarnations"of God in the other books mentioned above, are at best, not fully acceptable to the modern mind. Instances in the Ramayana are the killing of Vali & trials of Sita, not to mention the anthropomorphic viewing of monkeys & bears. In the Mahabharata, the role of Krishna in the demise of Karna & Duryodhana are also problematic as is the Gita which supports caste based occupations.
Though a part of the Vedas, the Upanishads rise triumphantly above all these region, religion & time based limitations to preach a truly universal & perennial philosophy.
In the Chandogya Upanishad, Satyakama, though of obscure origin, is deemed fit to receive spiritual education, blowing the caste system sky-high to smithereens. Also mentioned in this Upanishad is the story of Svetaketu, who is taught an ancient version of what later became the Atomic theory, that of subdividing matter into minute particles.
Most important & relevant now is the Mundaka Upanishad, which says "Considering religion to be observance of rituals, the deluded remain ignorant of the highest good. Having enjoyed in heaven, the reward of their good works, they enter again into the world of mortals. (back to zero!) But those who practice austerity (voluntary poverty & celibacy) & meditation in solitude & silence, attain liberation."(the true goal of human life.) The universality of this last exhortation is underlined by the fact that Jainism, though non-vedic in origin, subscribes to this belief.