The sets and sfx are the least of Trek VI's problems. I used to love this movie, but it has aged horribly. The story is very dated, the editing is horrible and the film does have a low budget cheap feel to it. The "cute" little jokes like Vulcan proverbs, and Klingons quoting Shakespeare are just dumb. If I can actually make it to the end, I need a barf bag when the cast mugs for the camera after saving the day at Khitomer.
This.
I'll also add the flimsy Galley set and Chekov's awful make-up to the list.