I've recently had a few clients who wouldn't do their homework.
They wouldn't tell me their preferences. Getting them to talk about what they like and dislike made me wish for Sisyphus' stone. They signed their contracts and gave me money, but didn't seem to understand that design happens within a full ecology, not a vaccuum. Being a helpful person, I tried to do their job for them. I've been down this road, so I know it's often futile. I came up with, and presented, a "catalog" of ideas. And surprise surprise, none of it looks good to these clients. How can it? Birthed in isolation, the ideas have no connection to them.
When I reach this point in a one-way relationship, I know I've already earned my deposit fee. I've put in hours to try to get the clients on their own side and to help them understand the design process. My next step is to risk "losing" the job. I'll send a message that says, as politely as possible, "I can tell you're not ready to take this seriously. Perhaps we should stop now, before you spend any more money."
It's important to be unattached to the response to that message. It's nothing more than a statement about where the project currently sits, and a query about whether to move forward or to abandon it.