I started a similarly titled thread a few months back.
I immediately concluded that I was not qualified to be a rater (me... building architect, mid single digit handicapper, life long self taught golfer) because an individual would have to travel the world ... Au, NZ UK etc and be of independent means (no need for a regular job, no family etc).
In my view, there are maybe 15 qualified golf course raters in the world.
It is very clear to me that many raters are in a formulaic rut.