You don't even know how the privacy works, I've heard of cases of it being traced but even if it is private, another more private network can come around but if they are not holding value then they are useless because you will either have money that keeps trending to zero or you will need to swap it to better money which compromises privacy, Bitcoin layer 2s have a better chance at privacy, especially as the network grows and utxos are not used that much because a Satoshi is worth so much