Try exporting CAD Nurbs models into Blender. Very difficult and for some objects there’s a ton of cleanup. That’s because CAD programs have a different internal data representation than mesh surface modelers like Blender.
And CAD of course works great for superior accuracy, something which polygon modelers can never quite achieve. With poly modelers, renders are much faster overall and they create much more topologic meshes which work better in games and animations.
And SketchUp also has a different internal data model then Blender, so of course there are going to be translation errors. SketchUp does realtime surface Booleans, which allow it to create simple looking models and for it to render in a specific way.
There are huge and wicked problems trying to accurately and perfectly convert everything to Blender, not the least of which are custom split normals. Somewhat similar to the issues CAD model conversion faces.
FWIW, I think SketchUp files convert admirably.
If you really want to do the best job (but not even perfect) at 3D conversion, get Polytrans by NuGraph.