With installation of course experience counts, it separates the wheat from the chaff.
On call and servicing is a different story, logging into a panel and isolating a fault isnt rocket science. Walk testing, checking panel voltages, batteries, monitoring, and sounders is also relatively simple.
Fault finding also requires a bit of skill, common sense, understanding of circuits, and detection. Experience helps a lot, it can halve the time of a breakdown when you know common causes, and less common causes.