There is something, somewhere out there, that is "ki". Once we find it, we will know. Till then, there is no replacement for the real "ki" made of "aaaa-eeee-iiii-oooo-uuuu", if we want to keep aikido alive.
Ki exists - only I know I did _not_ meet it yet, and also many persons I see who pretend they know what it is, actually don't. That was my point.
Kotodama practice is the Shinto equivalent of pranayama practice. Just because your experience with it seemed meaningless, that doesn't mean the practice itself isn't valid, just that your kotodama teacher was (apparently) less gifted than your pranayama teacher.