If TV ads were free
If ads had been free, then the way people would have learned how to do TV advertising would have been by running ads. If they were free, why not? Why talk about it if you could do it? Why guess what would work if you could actually find out for yourself? Running ads would have been cheaper than focus groups. But ads weren't free in 1964, so people talked and pontificated instead of actually running every ad they came up with.
You guessed it: new media is largely free. So why teach it in school as if it were a scary theory? Why encourage people to be afraid? Just do it. Build your own platform. Appear in the places that seem productive or interesting or challenging or fun. Experiment quietly, figure out what works, do it more. No need to be a dilettante, and certainly you shouldn't spread yourself too thin or quit at the first sign of failure... but... quit waiting for the right answer.
By the time we tell you the right answer, it'll be too late.