Anonymity is not a binary. Monero, even with the addition of RingCT, is vulnerable to transaction graph analysis (intersection attacks) that can de-anonymize users. Zcash takes a completely different approach that achieves ledger indistinguishability -- shielded transactions in the blockchain have no apparent relationship with each other, which is an essential privacy benefit.
Much of what I read in that thread is wrong or misleading: Monero does not have a trusted setup, but it's important to note that a failure in Zcash's setup does not disrupt the privacy of the system. The "poison-pill" vulnerability is not a concern in our system. The claims about the anonymity set are very misleading. It is possible to do far more than multi-sig in our system, we just haven't implemented it yet. The point about mining is specific to the paper and is irrelevant.
There are downsides to the system, such as our performance problems, but they are solveable given time. Zcash is obviously not the only player, but it's also going to continue to grow and adapt and improve, just like other cryptocurrencies will.