Almost all Acharyas divide the Vedas into two parts: Karma Kand (as explained by the Purva Mimamsa sutras) and the Jnana Kand (Uttara Mimamsa sutras, aka Brahma Sutras). The Samhitas and Brahmanas texts form Karma Kand, and Upanishads and Aranyakas form the Jnana Kand. The Karma Kand deals with rituals and worship of Devas, and Jnana Kand deals with Brahman and Moksha.
But since Moksha is more important than rituals and temporary material fruits, why are the Vedas overwhelmingly focused on the Karma Kand portion? The Samhitas and Brahmanas section make up the bulk of the Vedas, and not the Aranyakas or Upanishads.
Is this because most traditions and lineages have retained the Karma Kand portion more rigorously than the Jnana Kand? There are only 13 or so major Upanishads that have been preserved well, and the rest of the 108 haven't. So, if the full 108 Upanishads were properly retained, would they be equal to or be larger than the Karma Kand portion?
More of the Jnana related texts are found in the Smritis: Bhagavad Gita, Vishnu Purana, and Bhagavata Purana.