I used to subscribe to that theory, but no more. There was a time when CW
was the best mode for weak signal work, but as of my last experience (1990
or so) AMTOR had it beat hands down. I hear that AMTOR has since been
replaced with yet more efficient digital modes.

Sure, if you hoard a few kHz of your bandwidth for your
mode, you're certain to have better data transfer integrity.
The U.S. military has some real bandwidth hogging modes
they use. You're comparing apples-n-oranges to compare
CW to even AMTOR. You should realize that! Are you
trying to support your feeble point of view through deliberate
misrepresentation or are you really this ignorant of radio
emission and spectrum occupation? If it's the latter, I hope
you're no longer licensed or on the air.