Oh no, lets not start that debate again
Personally when cruising at 300kts and someone is coming at you at 300 kts, my eyes won't see them until it is too late
You may relax. Nobody has started any debate, as there's none to be had. There is no substitute for looking for traffic.
You'll note that I previously correctly stated that one should use all the resources available to look for traffic, as well one should. None of them relieve one of the responsibility to be heads up and looking for traffic. Even at 600 knots closing speed.
TCAS has never been a replacement for see and avoid and was never intended to be. I've never met a pilot who actually thinks that it is.
I surely have. More often than not, when I hear someone alerted to traffic, the response on the radio is "Got 'em on TCAS." Not "Traffic in sight."
Gimmicks don't replace the eyes. They supplment them, but don't replace the responsibility, requirement, and duty to stay eyes-peeled for traffic.