Low quality edit. it is important to make a quality and understandable edit so that people don't get bored and quit the video without keeping the video duration too long.
Not targeting the audience. Beginner YouTubers are trying to do something for everyone without determining their target audience, I recommend that you determine your target audience and create content based on their interests.
Using a bad title and description. Title and description should contain keyword phrases that summarize the content of the video. Therefore, carefully create your title and description and do keyword research.
Doing self promotion. I wouldn't recommend it because it's usually poorly received by other people, like adding your own videos to other YouTubers' comment sections to promote your own channel.