Based on K. Atlas's review only the initial prototype of Darksend was based on gmaxwell's conjoin.
Since RC4 Darksend+is still based on the CoinJoin protocol, but improves user convenience by turning the mixing process into a background, passive (but still online) process. This approach can be described as ahead-of-time (AOT) mixing, as opposed to the customary just-in-time (JIT) mixing typical of most CoinJoin implementations today.
And, as far as I know, the traditional Coinjoin relies on a centralized unity, whilst Dash's mixing relies on p2p nodes (MNs).
So saying darksend is a broken coinjoin implementation is a false statement, correct me if I am wrong.