The proposal is a 23% sales tax, with rebates per household to cover the additional cost of taxes on basic necessities. So, it's not "wildly regressive" and it does cover the current amount of revenue.

People don't like or understand the current tax system, so how would it be ethically different to replace that with another system they don't understand?

There's a whole literature on optimal tariff rates. For a large country, it's not right to assume that the world price stays the same after tariffs are levied. The reduction in quantity demanded from the importing country drives down the overall price, so the ultimate price paid is higher, but not by as much as the tariff rate.

Btw, I tried to zap your comment, but it doesn't appear to be going through. Is your wallet malfunctioning?