Monero also has "cryptographic privacy" when it comes to hiding transaction amounts, for example. Describing it just as a coin mixing on chain sounds too simple, something like Dash.
There are also realistic longer-term possibilities for L1 scaling of Zcash, including the possibility of doing a Coda-like succinct blockchain (https://codaprotocol.com/). I've been working on optimizing recursive validation (https://github.com/zcash/zcash/issues/3425) and researching how to find more efficient pairing-friendly curves in order to make this practical. Networking optimizations and other consensus layer upgrades along the lines of SPECTRE/PHANTOM (https://medium.com/@drstone/an-overview-of-spectre-a-blockda... and https://medium.com/@drstone/an-overview-of-phantom-a-blockda...), etc. are also quite feasible.
It's correct that we're not running anywhere near capacity at the moment, and that gives us time to develop these solutions.
-- Daira Hopwood (Zcash developer)
And Coda looks incredible if that can be done
Additionally, I wish Stallman would research for himself instead of asking an expert, but oh well.
They’re both great experiments and Stallman would be more impressive proposing better solutions than just sniping at the projects.