Radio is no excuse for not having a comprehensive lookout.
i had an air miss whilst instructing with a guy joining supposedly 300 ft above me ..he had forgotten to set QFE and had transmitted his altitude as height above airfield.
I had an air miss leaving a holding pattern, another in a holding pattern and two DC9s were saved from a collision on final approach by a colleague seeing the belly of the other aircraft through the eyebrow window.
20 years ago I spoke to an ex instructor who had a comprehensive aircraft company in the alps..he had stopped instructing because of the amount of collisions caused by the proliferation of electronic aids which led to fewer eyes outside of the cockpit; it’s no surprise that FLAM is now mandatory in the alps and even paraglider pilots are using similar collision avoidance systems.