Use “VectorPoints” to declutter a vector field plot by reducing the number of vectors, and “VectorScaling -> Automatic” to make shorter vectors shorter and thinner in the plot.

VectorPlot3D[ {-y, x, -z}, {x,-1,1},{y,-1,1},{z,-1,1}, VectorPoints->6, VectorScaling->Automatic ]

Cleaning up the plot unfortunately doesn’t clean up our example of a field of supposedly unit-length vector oriented outward from the z axis.

VectorPlot3D[ {x/Sqrt[x^2+y^2], y/Sqrt[x^2+y^2],0}, {x,-1,1},{y,-1,1},{z,0,2}, VectorScaling->Automatic, VectorPoints->4]