"I just don’t like it."
Why? Because they're not explaining WHY they don't like it. Perhaps because they don't want to hurt the designer's feelings.
However designers are professionals and used to receiving feedback, and if doing a revision then they need detailed feedback. This means the client needs to talk about specific parts of the design.
- color scheme
- special capabilities/integrations
It is a case wherein designers might even have to send a happiness survey to clients in an effort to find out what aspects of the design they don't like, and to remind the client it is okay to dislike elements of the website in the initial rounds of design. But the designer needs the feedback if they are to build the website the client wants.
Sometimes what the client really wants is a website that looks more professional, but for some reason they insist on having a cheesy looking duck on the page. The duck isn't helping, but efforts should be make to make the duck look chic and classy as opposed to lame and silly.
"Oh and can you make the colours of the website match the duck?"
No. No. That is just wrong.