Earlier quoted context omitted.
Elaborate. Your statement says nothing but "I'm a software engineer so believe me what I say Slack app sucks'
Analysing monero traceability is hard. Early wallets picked addresses to use in bad ways. A lot of academic work us needed. Luckily ZeroCoin exists.
It's a bit like a game of sudoku. A mixin input could have 4 different coins, and technically you can't be certain from the signature which is the real input. But in reality you can do downstream or source analysis and come up with probabilities for whether the prior transactions were authored by the same wallet, or associate with other keys used by other mixin inputs. Every little bit adds to the probability of two addresses being linked, and it really doesn't take many bits of information to confirm or eliminate mixin inputs as being real or fake.
This is notably different from how ZeroCoin operates, where the anonymity set is everyone and it is fully untraceable. However ZeroCoin has problems with respect to performance and deployment :\