Depends on the country. For countries with a lot of "black money" and corruption there is an obvious benefit. Taxes yield less because they don't capture the whole economy, as a result taxes are increased and get paid by the "idiots/ethical" which creates a vicious cycle. Now if tomorrow you had everyone paying taxes then 2 things would happen which would result in a new equilibrium. 1. The tax revenues would massively increase 2. People would push for lower taxes because suddenly they care more as their real marginal tax rate is the nominal one.

Would this result in more efficient spending of taxes in a corrupt economy? Not immediately. A lot of shitty people would get reach fast in the meantime, but the system would balance because people would no longer participate in the corruption directly as they used to.

Yes, you remove some freedom, but I am convinced that for societies that have a trust disconnection between the government and the people would be a net benefit (assuming democracy).