In general we don't expect religious systems to be static.

Certainly -- although Vedic deities are not entirely absent from modern Hinduism/Sanatana Dharma -- the prominence of different deities is very different. The Rgveda focusses largely on Agni and Indra, and yajna rituals (as opposed to modern puja-type worship) have a central importance. Shiva, assuming he can be identified as Rudra, is not invoked, but rather (being feared) appeased. And so on and so forth. So while modern Hinduism is not unrelated to the practices/beliefs of the Vedas (which I'm referring to vaguely as 'vedism'), it largely pays only lip-service to the Vedas. People might read the Gita, Ramayan, Mahabharata, but rarely the Vedas, which really only make an appearance in special ritualised situations (e.g. marriages involve some Vedic hymns).