Other cryptos are fully anonymous & untraceable. For example zcash uses zero-knowledge proofs (zk-SNARKs) to conceal all elements of a transaction (sender, receiver, amount.)
Zcash only uses those for some transactions because the complexity is so high. It also requires connecting to the payment network via an IP address, which isn't really anonymous.
No, Zcash offers the option to always use shielded transactions, if that's what you want. The choice to use a shielded or unshielded transaction rests solely in the hands of the user.
Private transactions are not the default behavior, which makes transaction analysis more feasible than with private-by-default currencies like Monero.
Also, zcash has the trusted setup issue, which requires that you trust the developers were not compromised or did not store data during the setup, or they might be able to print infinite coins without detection if the data were to be recovered. For some, this makes it a non-starter, despite the efficiency of SNARKS over Bulletproofs which Monero now uses.
Don't let that deter you though. Zooko only pays himself a $300,000/mo salary. He will struggle to get by without the crowds of new adopters.
«Private transactions are not the default behavior»
There is no "default" behavior. The software gives you the choice between shielded and unshielded, and the enduser has to choose. There is no default.
«requires that you trust the developers»
Not really. In the latest Powers of Tau ceremony, there were 87 participants. This group spans more than just the developers. Even if 86 participants were malicious or compromised, as long as there is at least 1 honest participant, the system can be trusted.
«Zooko only pays himself a $300,000/mo»
Not sure why this is a problem. By comparison, Satoshi "paid himself" (mined) 1M BTC =~ $6 billion dollars. I'm fine with the founders of world-changing cryptocurrencies being handsomely rewarded.
