Firstly the RA in RADAR stands for RAdio which covers significantly longer wavelengths than the visible light (an in some cases near infra-red) which cameras can detect.
While light and radio are both part of the electromagnetism spectrum they are different parts of it and not interchangeable. While they are all part of a spectrum in terms of physics, from an engineering perspective they might as well not be.
Equally there are laser based systems analogous to radar, usuallly called LIDAR
Also radar implies a device which is capable of deducing information about the range and possibly speed and direction of a target object, most cameras can't do this, or if they can it is through a separate system. In fact the auto-focus on most cameras is more akin to the optical rangefinders widely used for military purposes before the advent of radar.
A radar system consists not just of an emitter and receiver but also the processing equipment to deduce the required information while a camera is intended to capture and store a 2D image.
The closest thing to a 'radio camera' is a radio telescope. A key point here is that the differences in wavelength between radio and visible light means that a radio telescope is very different from any camera in terms of both scale and structure.
While radar and cameras could both be described as devices for detecting electromagnetic radiation that about as far as the similarity goes and is not a complete definition of either.