The problem with this convo is that there is a discrepancy of an ought from and Is.

But from what I understand, you support the existence of fiat money.

About the aggregate demand, just like Keynes mistakenly advocated. Saving and investing are unrelated activities in the Keynesian narrative are not two sides of the same coin. Because investment is sensitive to interest rates, an increase in the reservation demand for money can cause the interest rate to be too high, attracting more savings that are not realized as investment. As a result, investable resources go unused.

In your case, The Government spending through fiat money or let's just say a nuanced method such as quantitative easing, is just another coercive way unlike buyers and sellers in a market to establish a monopoly over the monetary system.