You are wrong. There are a small band of conspiracy theorists that good communications can not influence. The type who hang out on David Icke forums. But good communications can stop conspiracy theories becoming mainstream. There is a lot of good research in this field.
You forgot about the ones who hang out with Christopher Bouzy. The Sussex Squad, and those who gave him a platform on their Netflix documentary to peddle his wholly inaccurate report about online activity. And stand by while he continues to spout his unsubstantiated bile in the greatest form of hypocrisy there is - doing himself what he claims to decry.
Considering the vast number of conspiracy theories all over the internet about the Sussexes, I assume you think they are abject failures at communications and PR too.