Monero gains a little privacy by sacrificing scalability. Grin is designed for simplicity, scalability, and fairness, not privacy at all costs. In such a design, the optional CoinSwap protocol for untraceability is a scalability preserving feature.

Ensuring the correct recipient and purpose of payment is not only robustness, but also added privacy since payjoins obscure the direction of payment, something Monero lacks.

With only 4 effective decoys, Monero's privacy is deficient, while Zcash shielded txs enjoy far superior privacy, independent of all the transparent txs.