It’s rare that anyone would be using this, but just in case you are that fringe case, here you are: https://github.com/deranjer/blender-fbx-export-materials
Literally just changes the blender FBX exporter to allow the option to delete materials on export. Nothing else.
Check the releases tab to download the zip.
Just overwrite your old FBX exporter. This adds a new tab in the FBX export options for materials, with just one option “delete materials”. This will delete all of the materials on your object when you export. Rarely useful, but sometimes helps with some texturing programs (sometimes you create an ID map in blender, then export the ID map to your texturing program, but don’t want all those seperate texture sets).