Depth is information
Translucency works best when it explains how surfaces relate to one another. A softened layer can tell us that one piece of information is temporary, closer, or dependent on the material beneath it.
When every surface is translucent, that relationship disappears. The effect becomes atmosphere rather than structure, and content begins to compete with whatever sits behind it.
Blur with a reason
A useful blur preserves the sense of place while reducing detail enough for foreground content to remain legible. Navigation bars, temporary controls, and small overlays often benefit from this balance.
The test is simple: remove the blur. If the hierarchy becomes less clear, it was doing real work. If nothing changes except the mood, a solid surface may be the more honest choice.
Keep the edge visible
Translucent surfaces still need boundaries. A quiet stroke, a change in luminance, or a restrained shadow helps the eye understand where one layer ends. The result should feel calm, not fragile.