I'm unsure if I'm doing anything wrong. But in the 1.12.1 version, the extractors only extract end products from all furnaces and machines (any mods that work with belts).
Now in 1.16.1, belts extract ores and fuel as well. This renders the whole belt system unusable.
Tested with both vanilla furnaces and Industrial Reborn. Same result.

Vanilla furnaces have their output on the bottom. Use a hopper.