If your model has a lot of geometry, then yes, that’s probably the issue.
In general when you sculpt in blender you tend to have a lot of topology, and most of it unnecessary. You can either retopologize or use a modifier to reduce the number of polygons (I think it’s the Decimate modifier).
Have you checked the vertex count or the face count in blender? If you have more than a couple of thousand polygons you might have to reconsider the cave, and drastically lower its quality (reducing the polygon count)