Long intros. Intros in general. I went to film school and feel like intros are important in movies, not motovlogs. Netflix skips series intros for a reason...
Brand is good, but I'd rather see a watermark or a sound (aka BVG) than a video intro.
Bad sound. Can't stand bad sound. I am guilty of this in some vlogs, probably one of the reasons I haven't gotten far. But I barely have time to make vlogs, much less watch those that have crap audio.
Long pauses that aren't important. Just lazy editing. I'm totally guilty of this.
Boring, everyday content. I get it, life sucks. We all deal with traffic, go to work, eat food, etc. I am also guilty of this 'summary of what I've been doing'. It is a bit different since my channel is less than 50% vlogging so I like to update people in between my other productions, but still. Boring.
if I've never seen you before - stuff that is too personal without some reference or background. Yes you want to take care of your subs, but you also want to gain people's interest. Give at least a little blurb of where to find out more info or a small summary. Not enough to bore your regular subs, but a little bit to intrigue the new potential.