Can you give some examples that turned out really well? The ones I tried are exactly what comes out when I prompt the ‘bare’ gpt4 or gpt4o with the same prompt that I give your gpt.

Edit; scratch that; with 4o and the same prompt I give your gpt (for instance the example ‘Generate a UI concept for a fitness app.’), vanilla 4o does a vastly better job and continues to do so far even after some more prompting.