Sure you can, people do it all the time, but I'll grant you that it kinda sucks (which is how I notice that people do it all the time). There are situations where everything you want to reflect is already on screen and the angular difference between the camera and reflected camera isn't enough to be noticeable. When those conditions are met, SSR is awfully tempting. Water is the usual suspect, but wall-mounted mirrors can work too if the camera will only see it from glancing angles and it's reflecting a wide-open space.
In blender eevee render that's famous for screen-space magic you can get realtime mirrors with "reflection plane" "light probe" by placing it over the surface that's supposed to be a mirror.
