Leaking unnecessary data is detrimental to that anonymity. If I naively send/receive Bitcoin my counter party, and anyone looking at the blockchain, can see amounts and past/future interactions with other addresses. Every additional point of data is another piece that can potentially aid in unmasking you over time especially combined with other information offchain. Not even Monero is a silver bullet much less Bitcoin.

But agree that the fiat KYC bridges are the largest (but not only) problem