It's possible to do some quite clever things in more recent versions of qgis2threejs.
Objects don't have to lie on the DEM, they can float above them (using a constant or a numeric field value), such as in the setting shown below...
Things like wind turbines can be used for point symbols, if you use the COLLADA 3d format (e.g. exported from Blender or Sketchup)
For example, you can make "trees" by adding spheres slightly above the ground, and cylinders on the ground.
For example, the blog post Further adventures with 3D GIS by Nicholas Duggan shows what can be done and how to achieve it.
You can't animate them, though, so I doubt you can make your wind turbines rotate ;)