This is only true for mass production, where the set-up costs are spread across thousands of units. For small batches, the cost of automation often exceeds the cost of the batch itself. CNC machines are not magic; they require qualified and competent staff.
The same applies to quality control, fitting and assembly.
I don’t think they’re planning to start mass producing of SR-71s.
> because the job had become obsolete
You are greatly underestimating the number of parts, welds and inspections carried out on critical equipment that are done by hand or in small batches by highly skilled workers. The fact that they use a CNC machine does not make their job obsolete. In fact, quite the opposite is true, its require more skills.
Apart from the turbine section, virtually nothing on a helicopter is produced with a high level of automation or in large batch.