In an overall sense with this thread, I think people are focusing a bit too much on the individual specifics, especially as it relates to them personally. But that's ok, my topic was a bit vague to begin with.
My overall point is, what does difficult MEAN to you? A higher score? Difficult shots? Repetitive shots that you struggle with? Etc.
When I played my favorite course, Oakmont, I shot about a million.
Seriously, probably 15 or so shots higher than a normal course for me.
What I didn't do was lose many balls. Or have even one time where I struggled to figure out where I should drop. It was simply relentless in asking for an additional shot, here, there, everywhere.
I will use one hole, an often overlooked hole at Oakmont, to illustrate. On the 11th, I hit a 3 iron off the tee, one of my better tee shots on the day, up the left side, on the first cut of rough, not the deep stuff (about a yard or two from where the caddies were standing - and not a one jumped. I guess they didn't think I'd be that close to a fairway in regulation). I then hit a 7 iron, IIRC, into the left greenside bunker. I hit that shot pretty sadly close to the lip of the bunker and the hole location was middle left. My gracious host warned me that I should hit well above the hole. Instead, I opted to blast out to about 3-4 feet from the hole. I was proud of my effort. When I finished raking, I climbed up (yep, it's steep), and asked where the ball marker was, assuming someone marked my shot. My host pointed to my ball, which had drifted down to about 25 feet below the hole. From there, I two-putted for bogey, and I was given about a 3 footer for that bogey (I never want to slow down others, so I graciously accepted the concession).
I considered that a win. Many would call the shot result unfair. But that's what Oakmont demands: the proper choice AND the proper execution. And Oakmont is relentless in asking this repeatedly, on every shot, on every hole. What Oakmont doesn't do is repeatedly ask you where to figure out your drop should be.
Is Oakmont "too hard"? Not in my book. It is perfect, in my book. I don't expect a golf course to not differentiate between my poor thoughts/shots and a better golfer's thoughts/shots. On the contrary, I expect a great golf course to illustrate separation between the two. And I expect the golfer to understand the difference.
But few do.