This impression/idea has occurred to me several times in the years since I played Crystal Downs. I think I may have found the words to explain it.
Soon after I'd played the course, I had occasion to speak to two industry professionals whom I respect very much and who know the course very well. When they asked me about CD, I fumbled for words.
Yes, I had enjoyed playing, and knew that I was supposed to appreciate, the many and varied Par 4s that everyone (including Ran in his profile here) seems to focus on -- but for the life of me, I couldn't really recall any of them to mind, or should I say, they were not what stood out for me.
Instead, along with the great Par 5 8th, what I remembered best, and most fondly, were the Par 3s. I think I can now better understand/articulate why, i.e. it is their simplicity, and their (seeming) lack of planned and overt architecture.
Individually (except for one of them) the Par 3s at CD don't unduly impress upon first viewing; and as a set, they are rarely mentioned as exceptional. But:
The 14th: 140 yards of sheer loveliness, with a bunker protecting the front of the skyline green.
The 3rd: 160 yards, downhill, with the wind influencing club selection into an angled green.
The 11th: 185 yards to a tough multi-tiered green.
The 9th: 160 yards, uphill, to a green the runs away from you.
That's it. That's all there is to these Par 3s; but what wonderful golf they provide and wonderful golf shots they require, and all with an understatement of design and a modesty of purpose that makes them very appealing.
Par 4s are my favourite pars in golf, and the Par 4s at CD are indeed varied and interesting and excellent. But I found that, for my tastes, I could too clearly sense MacKenzie and Maxwell "thinking" these Par 4s into existence, could too clearly see the architectural options they "designed" into them, and could too clearly feel them bringing their "ideas" to bear.
Does that diminish them as golf holes, or diminish their greatness? Well, I'd be loath to say "yes" to that -- but I do think that in general when you can "see the hand of man" at work it usually means that there is a lot less subtlety involved than there might otherwise be, and (over time and multiple plays) perhaps less interest/engagement too.
Were the Par 3s "designed" as well? Yes, of course -- but in their apparent simplicity there is not only beauty but also a lack of reliance on the overtly clever aspects/architecture of the Par 4s.
I'm not sure if anyone will agree with me, and certainly I won't argue that I'm "right" -- but this is simply my attempt to put into words the experience I had playing Crystal Downs.
Peter