Maybe you should stop banging your head against those walls it may assist your understanding

The days of those moves are gone because the days of anyone doing a single axel in a competitive programme are gone and went in the 80s. Once figures were gone and free skating was king we never saw skaters do them in competitive programmes so again I would say it's got nothing to do with COP.
And the bolded statement simply shows how clueless you are about the judging system. Have you even read the rules? Why would a skater get negative GOE for completing a single jump? Skaters don't get negative GOE on a jump unless there is a problem in the
quality of the jump. The base value would be the base value for a single axel. The modified air position (for a tuck axel which I think is the jump you are discussing) would likely get positive GOE, and using the example of Robin Cousins back in the day I'm certain the speed and flow into and out of the jump coupled with the tuck would likely get him +2 or +3 in GOE, but only on the base value of a single axel.
And while it is almost certain that a skater at the senior level is not likely to ever intentionally try a tuck axel in competition because of the lack of points, I would hardly say the current judging system is any different to 6.0 in the 15 years prior to its implementation as i cannot recall any skater in the 90s including a tuck axel in their programme.