Earlier quoted context omitted.
And a major reason workers are spent out is because of high rents. If the US would build enough housing in the major employment centers that the highly skilled workers wouldn't spend 90% of their after-tax income on fixed expenses, they'd have more money to spend to drive other businesses. All the disposable income is being sucked into rents, and eventually that will make the economy run slower and slower, fewer sale…
You are assuming the answer. (The old phrase for this was "begging the question"). Someone could easily ask "Why don't the landlords, who get all that money from rent, spend it on something, and thus drive growth?" And you can easily answer that: the wealthy spend less of their income, they save more, therefore the high profits from rent increase the savings glut, etc, etc, etc. But you should state the answer direct…
Most wealthy individuals aren't holding cash, they put the money in a savings account or investment that has a return. This money appears to be held to most people, but even money in a savings account makes its way back into the economy by affecting the reserve requirements of banks. Its a proportional effect, because reserve requirements are greater than 0% but lower than 100%, but it still contributes.
If they actually are hoarding, the question is why and in the past that is usually because savings returns and investment returns are expected to be negative. In which case, thats the problem to solve.