We also have no true capital gains tax. Without this, GST is practically the only way we get tax from the ultra wealthy, right?
This is a major problem with flat taxes; the ultra wealthy pay a tiny portion of said income/wealth in GST; vs the poor who pay a huge portion of their income in GST.
but that seems to also be making the system more complex by balancing tax collection against subsidies for the same thing
Not true; complicating GST, complicates it for all businesses. It adds compliance overhead to everyone; even though it would be minimal extra for most businesses, it is not zero. Not zero multiplied across all businesses is still millions in compliance dead weight cost.
So do we just hand cash to supermarkets to make certain products cheaper? This seems more complex than just removing GST.
A targeted subsidy; could be applied at the producer end, making the bureaucratic overhead much smaller. Thus giving NZ producers a leg up compared to overseas producers.
This isn't as anti-competitive as it first seems either. Since feeding ourselves is a national security concern. It behooves us to prioritize local production, even in the event we have to subsidize production.