Currently, the Plasma Desktop only allows positioning of icons on a strict grid basis. This is a bit inconvenient, in the following terms: 1. The desktop violates the user's action of positioning an item on a specific location. User can reposition items explicitly when desired (via an Cleanup/Arrange action). 2. It feels like the software is like a mother constantly cleaning up after her children. 3. Desktop, for most folks, is a real workspace. We arrange icons, according to the things that we work on, we sometimes group them on specific locations on the screen. Without spatial positioning, this does not quite work. 4. It is familiar for folks that use operating systems like macOS and/or Haiku. This will make them feel at home with Plasma.
You can do 1-3, just aligned to a grid.