Elevation change in disc golf can (rarely) turn into too much of a good thing. Finding a balance between the two is part of what makes a great course. One of my favorite local courses, Orange Crush, has an epic stretch from hole 10 to 16. Hole 10 is a gentle/long downhill, 11 is a pretty steep one, 13 is another steep downhill, and 16 another steep one. Any one of these could be a signature hole at most courses nation wide, as those excellent steep downhills are some of the most memorable on the course. I've always just accepted that some of those holes (12 in particular) are bound to be "ordinary" or maybe less enjoyable/memorable because you need to gain elevation again.
Now the OP is getting at the philosophy of uphill versus downhill. In terms of course design, well-designed uphill shots fill in a course with a unique challenge while bringing us back to the higher tees. I respect that. There's one course I remember in southern California, Brengle Terrace, that seemed to go out of its way to prevent downhill shots. I think that made the course safer for pedestrians, but it was frustrating and even insulting as a disc golfer, because the design forced you to walk up lots of hills without being able to throw down any (okay, MOST) of them.
TLDR: if you're a designer, accept the challenge. Use the up of your hills just as well as the down.