Fusion 360 has poor STL capability, it chokes with over 50,000 or so facets. I have STL files with millions. The Vectric vcarve family or Carveco Maker easily can handle and toolpath larger STL files, but are not free. VCarve Desktop is $350 and has size limitations (24"x24") Carveco Maker is $15/mo or $90/year and does not have size limitations. There are some free choices like kiri:motod but I have not used them, VCarve and Carveco are very simple and effective.