1. If your scene fails to load, takes a long time to load, or runs with a low frame rate, it might mean that the geometry of the scene is too heavy.
Here you can find information about What is the scene size (polygons) limit?
First check the total number of triangles in your scene in the Scene statistics panel
of the Objects tab.
2. If your scene is too heavy identify the most complex objects
The Objects tab lists objects sorted by their triangle count, so the most complex object is at the top. You can see the number of triangles of the selected object in the Object panel.
3. In the case of a group object you might need to analyze the content of the group to identify nested complex object. To expand the group click on an arrow next to the object name. Then, check the triangle count of the nested objects. If necessary, analyze the object hierarchy even deeper.
4. Another important thing concerns high poly instances - Shapespark is reading all the tris. Even when you use instances your graphic card needs to render all the tris. So the only way to make the tris count smaller will be to optimize objects that are instanced.
5. Optimizing geometry in 3D program
These tools are recommended for optimizing geometry in 3ds Max and Blender: