SDFs are very neat up until the point where you need to build parts that have very precise specifications.

Something like two precisely interlocking gears with a tooth geometry with a profile that's the developed curve of the opposite tooth is a nightmare to build with SDFs

Or precise fillets.

Or hard intersections and differences.

Very useful for doing soft, squishy shapes, less so for hard CAD.

Also, a suggestion: in your project, please consider using Wavefront OBJ as an output format, it is a much, much better choice than STL (STL can't represent the actual topology of the object, it has to be reconstructed).