I agree with the sentiment but ironically your transliteration of the name of that language reveals that it certainly has undergone at least some sound changes. Why do people in the north pronounce the vocalic "r" as "ri" while in the south they use "ru"? Why do people in the north drop word final schwa but in the south they add a nasal bilabial?

While it's very easy to pronounce Samskrta in a way similar to what was likely used in classical times, there have definitely been sound changes to an extent.