DHD nerd here: Do you ask them other questions outside of the designer career prompts about their likes and dislikes? (Using Interests, hobbies or small talk to ask about favorites.) If a Sim dislikes, for example, the color red and you use a lot of red categorized items, that affects the way they react to the design even if you include things they ask you to do/not do in the main request categories. This includes every Sim in the house so be aware of that. The majority of the family should be okay or happy at the end of the design day. (This really depends on how big the family is.)
if you do all that, I’m sorry and just ignore me. I just find a lot of people don’t realize this about that career.