The worst thing I know is to watch those soapmakers that scrapes the bowl, the stickblender and scrapes absolutely everything for hours and hours, until the very last drop. And they don't stop scraping their bowls and utensils even then. That is very, very annoying. It is just cheap oils and lye mixed together, nothing very precious, so no need to scrape everything like crazy, and definately no need to do so when making Youtube videos for others to see. Or at least edit the fanatic scraping away.
I don't like videos where nobody talks and there is standard Youtube music instead, those annoying soundtracks you have heard 3 million times before.
I do like to see a lot of different style of videos. But I hate very short ones. 30 second to 2 minutes, no, those I skip immediately. I know I can't learn anything in 30 seconds. I prefer videos from 10 to 30 minutes.