It always seemed weird from Day 1 when I reviewed Monero vs Zcash to rely on anonymization that depends on other nodes and number of honest peers, instead of relying on technical anonymization that Zcash does, seems much more reliable and long-term workable, even though it was much harder and took them longer to arrive at good solutions.
If Zcash had privacy by default, they would have won against Monero for being the private cryptocurrency. As it stands, any private transaction on the Zcash chain stands out like a sore thumb and the use of de-anonymized transactions around it make it easy to figure out how much money was moved. It was a missed layer 8 opportunity on the part of Zcash.
This attack doesn't seem to work if you run a monero node, though.