This is exactly right; the reader/audience needs a way to enter into the story–without it the reader can quickly lose interest–and a likeable character is one of the easiest routes for that.
Character likeability is less important if there is another way into the story–say, the complexity of an intriguing and multi-layered plot, or a rich, engaging conflict of style/philiosophy between two or more otherwise unlikeable characters (like an argument that’s interesting even if you aren’t invested in either side winning).