People not spending money decreases the velocity of money, which effectively reduces the money supply, causing deflation. Similarly, the drop in demand itself acts as a counter pressure to inflation by simple supply and demand.
Not only does this not make sense as a feedback loop, but until the 1970s, the economic consensus was that it was impossible to have both high inflation and a recession at the same time. This view was only overturned when it happened, and the phenomena came to be known as stagflation.
In my opinion the velocity of money for consumer and retail products is more or less constant because a large portion of the population doesn't (or can't) save a significant percentage of their income, while the 'asset money' category like real estate and stock market is hugely affected by velocity of money driven by falling interest rates.
The unfortunate news is that most macroeconomic theories (including mine), especially the neoclassical variety, are kind of useless in the real world because of inability to actually implement policies 1:1 in the real world. The modeling errors are also quite significant. Nobody is really trying to solve NRAs(non reproducible assets) or monopolies. Everyone just assumes you can harvest more bananas or colonize a second planet.