Is it important to your religious tradition that modern people sound exactly the same as people from 2000 years ago?
Yes, it is extremely important.
Ordinarily at this point I would say this is why you should not speak on what you do not know. I would say go do some homework, and I would walk away. Because instead of asking this question at the outset, what practicing Hindus believe was challenged and virtually mocked by someone who barely knows the religion, if at all. But for the benefit of others who are not so confident in their “knowledge” I’ll explain.
In Hinduism sound is energy.
Shabda Brahman or Sabda-brahman or Nada brahman means transcendental sound (
Shatapatha Brahmana III.12.48) or sound vibration (Shatpatha Brahmana Vi.16.51) or the transcendental sound of the
Vedas (Shatpatha Brahmana Xi.21.36) or of Vedic scriptures (Shatpatha Brahmana X.20.43).
Nada Brahman or Shabda Brahman.
We communicate with our Gods through this sound energy... mantras, other Vedic hymns and chants. They must be chanted exactly as they were revealed to the rishis (sages) and perceived. A mantra has no effect if it’s not pronounced as originally received. There is some wiggle room because everyone has their own individual accent.
Even when an appliance doesn’t receive the full voltage from the electric grid, e.g. a brown out or faulty connections, it will still work to a degree, though not fully or as intended. The same holds true for Sanskrit. In liturgical use if Sanskrit is pronounced incorrectly or not as closely as possible to its original sound it creates a faulty connection. It may even do damage. Just like a faulty electrical connection.
If Sanskrit is used as a mundane spoken language, like any other language, near perfect pronunciation is not necessary. Nor is following the rules of sandhi in prose. Writing down sacred writings it is required. For personal use it’s not as important.
So yeah, it’s important in our religious tradition and why great care is taken to transmit it faithfully from teacher to student for liturgical purposes.