Why would you trust the transmissions you get? How do you verify them? If you get 50 conflicting messages, how do you deal with that? Which one do you go with?
Disseminate. OK, how are you going to do that without any other communications? Yelling, flyers, spray paint?
HF works fine if no one is messing with you, but you need structure, codes, and a network of people otherwise. And even then, that network is easily infiltrated. Occupied Europe is a good history of just how difficult and dangerous HF transmission and information dissemination is when the powers that be want to stop it. The one way coded messages of the BBC took years to make work (network problems) and were of limited usefulness and always suspect of having been broken.
Your occupied Europe analogy is about 70 years out of date.
Things move on.
Go out in the world and play hard for 20 years and tell me that HF isn't useful.
/johnny