[denton-scratch]

"two kinds of T's and D's which sound almost identical to me"

Sanskrit is a dead language. Nobody has used it as a spoken language for nearly a thousand years; and even those Sanskrit speakers a millennium ago were using the language only for specialist discourse, not as a mother-tongue. I'm saying it was already a dead language a thousand years ago.

We don't really know how English was pronounced in London, England as recently as 400 years ago. Shakespearean English might have sounded a bit like the accents of some relatively-isolated East-coast US communities (Amish?). We can only guess.

We have clerical Latin pronunciation, and legal Latin; the Latin pronunciation that I acquired was "school" Latin, which I think is the same as the pronunciation used by lawyers in anglo-saxon countries. but we don't know how Latin was pronounced in 50 BC (say). For ancient Etruscan, we can't really even guess.

There is no correct pronunciation for Sanskrit.

[svat]

The Sanskrit tradition is uniquely centered around language itself, starting with its origins in the preservation of the Veda. There is an ancient tradition of Śikṣā (≈phonetics) for the correct pronunciation thereof, and there are further detailed descriptions of sounds given by Pāṇini and Patañjali. Most importantly, there is still a robust oral tradition of reciting the Śruti (Veda), which has often been compared to a tape-recorder from at least 2500 years ago.

All of this is to say, we know very well (except for some much-debated rare words) what the correct pronunciation of Sanskrit is: it is what the Śikṣā śāstra says, what the grammarians elaborated, what is still heard at every Veda-pāṭhaśāla, and what is still spoken by at least tens of thousands of paṇḍits whenever they want to debate anything technical, or even just as a link language to make chit-chat across (other-)language barriers.

Sanskrit is as alive as it has ever been. It is “dead” only in a very restricted sense of the word — e.g. if you only consider usage as a mother tongue rather than as a language for poetry, technical topics, debate, etc — a sense that is irrelevant in the context of Sanskrit, because by this definition (classical, as opposed to the older Vedic) Sanskrit has been “dead” since the moment of its birth (its codification by Pāṇini, which was so exhaustive that it has become, for millenia, a de facto definition of correct Sanskrit), and you'd have to say that everything of value written in it was written after this moment of death/birth (including, according to scholars, most of the Bhagavad Gita itself). Oh and also, I personally know at least a few dozen people who can and do speak in Sanskrit routinely, and at least three families where Sanskrit is the children's mother tongue, and the primary language spoken at home. So the claim of “Nobody has used it as a spoken language for nearly a thousand years” is hard to take seriously.

In any case, the two kinds of Ts and Ds (retroflex and dental) are contrasting phonemes in Sanskrit, meaning that if you mix them up you'll get different words with unintended meanings — it would be hard to consider the outcome “correct”.