Is pure Telugu dead? It feels impossible to speak Telugu without using English/Sanskrit words.

 Whether it is pure or not depend on one’s perception. Language has to evolve as per the needs of the time, and nothing wrong in adding words from other languages as it is. This is true for all mainlands of any language.

If any one look to hear any timeline diaelect of ancient language, the best way is to interact with migrants to far away destinations.

For example, Telugus migrated to Silicon Valley in 1980s still maintain the language and culture of 1980s.

Telugus migrated to Tamil Countries still speak the 600 year old Telugu, but instead of English/ Sanskrit words their descendants may be using Tamil words.

It is more important that the other person understand what you speak, rather than checking the purity.