The original GUIs were all flat because that was the default. A button was a rectangle with text in it. A checkbox was a rectangle with or without an X across it. Pure black on pure white, no colors or shades. Windows used this style until Windows 95.
Nobody seemed to have a problem with it. It was largely clear what was a button and what was a checkbox. In hindsight it was certainly uglier than the 95 style (maybe just because I grew up with that) but it wasn't unusable at all. As you say, it was clear what was a button, what was a checkbox. I think it was because GUIs were mostly made out of standardized elements whereas today we have everyone trying to put their unique spin on every element.
The original GUIs were all flat because that was the default. A button was a rectangle with text in it. A checkbox was a rectangle with or without an X across it. Pure black on pure white, no colors or shades. Windows used this style until Windows 95.
Nobody seemed to have a problem with it. It was largely clear what was a button and what was a checkbox. In hindsight it was certainly uglier than the 95 style (maybe just because I grew up with that) but it wasn't unusable at all. As you say, it was clear what was a button, what was a checkbox. I think it was because GUIs were mostly made out of standardized elements whereas today we have everyone trying to put their unique spin on every element.