You can use cryptocurrency which hides all of your transactions (like zcash) and pay your taxes as a law abiding citizen. There is no conflict here. Tax systems rely on citizens reporting anyway.
> You can use cryptocurrency which hides all of your transactions (like zcash)
Nit: only if you use zcash shielded wallets(very rare & resource hungry) are your assets private. Most wallets use transparent addresses, which is kind of similar to normal ones.
Given current landscape, only monero is defacto private.
I am fairly certain that many citizens would be tempted to become creative in their transparency (or activities) if they knew they would never get caught. Such is human nature.
It relies on reporting and the right to audit, so they may end up with all of the information anyway; it's more that you are making them ask for it rather than providing it proactively.
ever heard of CRS (Common Reporting Standard)?
https://en.wikipedia.org/wiki/Common_Reporting_Standard