"A diode is not active by itself, because it's a two-port circuit. There is no
way for it to have an input which controls an output. "

So your contention then is that tunnel diodes, Gunn diodes and Zener diodes are not active devices.

If that is so, then a magnetron is also passive. It is technically a diode with an indirectly heated cathode unless you consider the magnet an element.. Also, what of the case of a Hall effct device ? Nothing electronic controls it, only a magnetic field. Other devices can have more than two terminals aqnd be passive, so where does the Hall effect fit in there ?