company i work for uses solidworks to make custom gym equipment and they send me a 150mb+ .fbx file to use for sketchup renderings. this one is 200mb and i cant get it to import with extentions, or even re exporting as a .3ds file either. it also crashes my computer every single time too
you might want to try skimp, they have a free trial, it’s quite good at importing complex models and lowering their polycount.