Disc Golf is primarily about shaping throws around vertical obstacles versus dealing with surface challenges like ball golf. So, adding vertical obstacles where necessary due to lack of natural obstacles like trees, bushes or mounds should be encouraged to provide at least some vertical challenges.
However, it was pointed out earlier that aesthetics is an important design element for enjoying the game. So ideally, either add natural obstacles or ones that look natural like the artificial foliage in zoo exhibits OR go the opposite direction and install all kinds of manmade obstacles on many holes like Flying Armadillo and Tiki so the aesthetic is a full-blown kitschy design. That can be fun and challenging, too. I think the concern arises when there are just a few jarring, unnatural looking structures, like this example, on natural terrain.