Well yes, the optimum number of full time jobs in a household is >=1 and <2. This isn't really a function of useless jobs existing or not, but more of a function of CoL and income distribution.
COL is itself a function of the prevalence of useless jobs. They increase the cost of everything, they increase the need for infrastructure, they create friction for real work, etc.
Put another way, if society allocates more resources to people who work outside the home doing useless things, then fewer resources are available to people staying in the home doing useful things. One way this manifests is inflation, ie, higher COL.
Put another way, if society allocates more resources to people who work outside the home doing useless things, then fewer resources are available to people staying in the home doing useful things. One way this manifests is inflation, ie, higher COL.