Dilemma between automation and manual execution is always a challenge for correct management decisions. It is not easy to decide, if an investment to automate a process will bring sufficient benefits and returns, especially, on a long term.
However, decision here should not be voluntary. There exist simple and reliable criteria to clearly distinguish relevance of process automation in every practical case. The criteria is process volatility. Volatile processes are difficult and impractical to automate.
Volatility of the process is easy to measure. Record multiple execution paths of the process. Build an average execution path. Measure deviations of each execution from the average. Measure volatility as median of these deviations. This will give uniform and universal criteria for processes of any nature and scale.
As a rule, volatile processes appear in new and actively developing business areas. With time, these processes become a routine and acquire better formalization. When formalization grows and volatility drops below certain level, it is clear evidence that a process is mature and stable enough to automate.