I haven't had this issue. I'm currently playing one Sim who lives in a forest and doesn't actually have any sort of housing structure, and she's not had any positive or negative moodlets about decor (she's struggling in every other department tho lol). Maybe it's all of the trees and plants around her so she's fine?
And the other Sim I'm currently playing lives in a nearly bare house with almost no furniture (but there is flooring and wallpaper) because she's broke and I'm playing it like all of her stuff is still packed up and she has to still order some large furniture. But all of her miscellaneous packed decor is in one isolated room. The rest of her house is literally one single bed in her bedroom, and a utilitarian kitchen and bathroom. She doesn't get positive or negative decor moodlets either.
What kind of decor have you been trying?