Why can’t a conventional (closed) oscillatory circuit be used to emit and register electromagnetic waves?

A closed oscillatory circuit is a system with lumped parameters. In it, the inductance of the entire circuit is equal to the inductance of the coil, only the capacitor has capacity. Accordingly, the magnetic field exists only near the inductor, and the electric field exists between the plates of the capacitor, that is, the electric and magnetic fields are separated in space and time.
The fields are localized in the contour, the radiation of electromagnetic waves is very weak. Therefore, a closed oscillatory circuit cannot be used for radiation and registration of electromagnetic waves.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.