w.r.t. your argument :
<<the Keynesian argument for demand “stimulus” -- that our economy's health depends on higher and higher levels of spending.<< my remark :
Keynes copied some of the ideas of Silvio Gesell, who understood the dual nature of money
1 exchange for goods and work
2 a means to store value for many years
these two properties of money lead to problems in economics/reality .
Property 1 is explained by a comparison to a heating system, water (=money) is pumped in a circle and the heating does its job.
If there is a big leakage of water (=money) the heating stops to work. If someone wants to keep some water (=money) for himself, the rest of society may suffer (jobless, to less orders).
Silvio Gesell designed a system, that already worked from 1000 till 1350 A.D. .
The suggestion of Keynes was, to not repair the leaky system and refill the water by the state and the taxpayer.
I have not met any engineer,
who would suggest such a b...s... .