I agree that it's just something that when you see it, you know what it is. However, I think that the ideal Disc golf course will have many more elevation changes than most have now. but the more artificial it is, the more gimmicky it will seem.
and I completely agree that mandos seem gimmicky, and when there is more than one part of a hole with a mando, I hate that. It's almost as if they were saying, "Hey, we didn't have a good spot for another hole, so we forced one in here with this mando."
However, a course is a course is a course. The only hard and fast rules of course design that I think should always be followed in every circumstance without exception all the time (is that clear enough?) is that the teeing area should be large enough that it is safe, and a basket should be low enough that it allows basically everyone a chance at a drop-in. ("Basically everyone" excludes short children and little people) Now, John Houck knows a lot more about design than I do, but I think that there is some place to break basically every other rule. So breaking the rules some equals something that is okay. But doing it over and over again makes it gimmicky. That's the best way I can describe what makes something gimmicky.