The term “Structural unemployment” has a technical definition and a colloquial definition. And authors frequently criticize the colloquial as not matching the technical, rather than the premise put forth by the colloquial. However, the colloquial definition is correct. That is, that there are people trained and experienced in skills that will not return to the economy, and that there are few if any sectors of expansion available to absorb them in any potential recovery, and if unemployed long term, they may be permanently ostracized from the work force. As an aside, it is unlikely that the USA will return to a consumer-debt economy. We will not be ABLE to. Not unless we play tariff and protectionist games, and deprive other geographies of their ability to arbitrage prices.
The high current level of liquidity is limited to the financial sector, and even there, to a narrow band of the financial sector. There are no savings going on anywhere, and instead there is debt reduction going on everywhere.. The country is operating at higher efficiency out of fear and necessity — a combination which cannot persist indefinitely.
So, the colloquial concept of Structural Unemployment is accurate in it’s usage.