The big problem with Workbench 1.x was that it looked like a toy. While in theory the colours were a good choice (high contrasting), it looked silly.
It didn't help that the UI was an inconsistent mess. For example, take a look at the format requestor, totally different buttons to everything else! Contrast that to MacOS which despite being monochrome looked much sleeker, and more professional, and more importantly had a good consistent GUI toolkit right from the very start.
