There are healthy economies that are more liberal than ours also consume less. Its not really a case like you pose it.
The goal of Keynesian economics isn't simply to increase consumption, it is to increase demand by giving people the ability to cover needs and buy things they would buy, but can't, which is what ruins economies. Food stamps aren't so you can import zebra steaks (if such a thing were to exist), but putting money into the economy that can be spent on food helps the economy move. The strength of an economy is based on its ability to meet the needs of consumer, during crashes, extra aid is often needed to do that, and on top of that if human needs reduced, so would the necessity of a large economy, but that's not how we live now.
However, you also need to realize that liberal economic plans are not based on unfettered economic growth at any cost, even the most centrist democrat believes in basic economic regulations that stifle business growth for, at a minimum, a perceived benefit for society.
Conservative economic policy is based on boom-bust type economic movement. They let things go, when people start coming up with crazy and sketchy ways to milk markets, they let it go, and you get booms, when it comes back to bite them in the ass, you get busts, and their policies encourage both.
The gold standard is regular for countless reasons, in the end, you are still basing your currency on faith, whether it being in the stability of the government or the belief that others will universally accept gold in trade at a stable value. Inflation relative to growth makes sense, though it is a touchy and difficult subject.