Nobody has proven that "perfect anonymity" doesn't exist. Maybe it exists but it still hasn't been discovered.
There are, for example, algorithms in cryptography that provide "perfect secrecy" (as defined by Shannon). Similar concept could be created for the anonymity of coin transactions. And somebody might find scheme (or algorithm) for anonymous transactions that will provide "perfect anonymity". Zero-knowledge-proof coins are coming close to this.
The main problem is still that that the promoters and marketers of this coin claimed that it provides "true anonymity" and similar things. Although the developer clearly stated that the "true anonymity" probably cannot be implemented on blockchain type coin.
Sorry i forgot to answer.
Even if you use this algorithm (for the transactions) you are vulnerable
the cia have minimum one method who permit to track your transactions (and it will continue for a longtime) i don't think that they will use it to track you or me, but i know that is possible so i know that you will not be 100% anonymous using dark,crypt,xc,ect,ect. (i talk about the cia but everybody can do it... with skills)
My english is bad but all is science, peoples who think that they can be 100% anonymous don't know anything about the science.