I think it depends on how well you use the format of the comic to convey your story as well.
Take for example Webcomic Name by Alex Norris. It's a 3-panel strip web comic in which they literally draw a blob that delivers, as they say themselves,"the same joke every time." It has a simplistic writing and art style, but Norris' use of color and details to bring visual variety, and the "oh no" joke set up has allowed them to create eye catching, easy to digest content and humor.
Another example is with the artist One and his One-Punch Man and Mob Psycho 100 series. While his art needs some improvement in some areas, the man knows how to entertain by intertwining humor, story, and character personality with a strong composition and paneling layout. Even with Murata Yusuke's rendition of his One-Punch Man series, they kept most, if not all, of the the original storyboard layout because it conveyed the message and humor of the characters and story perfectly from the get go.
Since you said that this is for a writing portfolio, you could add an extra/miscellaneous/for fun section for script and storyboard examples of your writing to showcase that you understand the nuance of bringing your writing into the comic medium. Or you could just create a portfolio specifically for comics altogether. But like @joannekwan said, only include what you feel confident with and know that you can deliver.
But yeah, don't worry about whether you think your art is bad. There are more elements to the art itself when it comes to comics and the only way to improve is to just get started and practice. I wish you luck with your work and decisions!