The main focus behind the change is to stamp out cyberbullying, but some of the changes include profanity and innuendos which a lot of genuine content creators all have.
YouTube wrote...
Content that is considered "not advertiser-friendly" includes, but is not limited to:
*Sexually suggestive content, including partial nudity and sexual humour
*Violence, including display of serious injury and events related to violent extremism
*Inappropriate language, including harassment, swearing and vulgar language
*Promotion of drugs and regulated substances, including selling, use and abuse of such items
*Controversial or sensitive subjects and events, including subjects related to war, political conflicts, natural disasters and tragedies, even if graphic imagery is not shown
They do go on to say graphic images are fine so long as there's an established context, but they also say "Don't promote your own shit or else advertisers won't like it" and "Don't put explicits (swearing, images) in your title or thumbnail". Considering YouTube's track record with how they deal with Copyright claims I'd say people's concerns that their videos will get demonetised because it's not deemed "Advertiser friendly" over technicalities aren't unfounded.