This is a non sequitur. People being economically redundant doesn’t necessitate a system collapse. It assumes our existing systems can’t handle an increase (assuming we have economically redundant people today) in those who are economically redundant.
Capitalism defines who owns the means of production scoped to the definition of ownership in a particular governance structure. In the U.S., for example, full ownership gives people the right to produce as much as they want with rules in place to seize the rights of ownership if broken.
One rule of ownership is that taxes must be levied on the positive return of capital. This today is what helps funds the welfare state. The idea that the system collapses implies we won’t be able to scale this welfare state up which seems unlikely to me.
There’s already a deficit caused by welfare spending. An increase in abundance (of work, resources, etc.) can reasonably alleviate this if we consider the possibilities in removing inefficiencies within the government itself and their biggest cost drivers like public health.