I don't think the courses need to be extreme, but they should be "cross" country. Meaning not road races, nor manicured golf course - though, of course, you might need to cross a road or golf course.
Let's not underestimate, though, even what you would call "easy" courses. I was a good track runner (Primarily 1500, but I could go up in distance), and I was a pretty decent road runner. I was terrible at XC and I ran on a lot of golf course like course. Or those which combined trail and road.
Something like 80% of my XC races where what I'd consider sub-optimal. Where only 25-30% of my road races were, and only 10% of my track races.
IMO, it was the soft surfaces which did me in. Just having the course have 20-30% soft grass or trails does a lot of people like me in.
Still, if you are the grinder type, you still need more advantages over the runner who can run a good golf course, but not a mudder course - and there are plenty of them as well.