So-called "shitty art" poses a hurdle to adoption but I find I stop noticing it entirely unless it's a fundamental part of the visual storytelling, in which case I would call it "distinctive." A
distinctive art style can change how the work is digested and interpreted (see e.g.,
The Medium Is the Massage), so for me, art that does not conform to expectations is just another tool in the artist's bucket. Pure style unsupported by quality writing can be fine if done well (like all Michael Bay movies, for example) and likewise excellent writing unsupported by quality art is more likely than not going to be memorable.
How to differentiate between shitty vs distinctive art? Gut level, eye of the beholder kind of stuff I guess. I would define distinctive art as something with a recognizable and consistent (reproducible?) deviation from norms, but...that's just the uneducated, armchair art historian in me reaching for leverage. Rather, let's illustrate it with a picture worth a thousand words:
(cue the Mr. Burns meme)
Three cases-in-point:
1) I love love (LOVE)
Sahara Mizu's work, but the
weird triangular hobbit-thingies ears of her characters used to drive me up the wall. These days it's just part of her artwork's distinctive charm.
2)
Afterschool War Activities launched with noticeably primitive artwork that grew in detail and quality over time, and the storytelling framework (that of a post-facto documentary_ was compelling/inspired enough to get me through that initial hump. I don't read too much manhua which is why this sticks in my head as my gold standard for evaluating lower-tier artwork at launch.
3) MangaPlus's recent addition
At Summer's End would ordinarily fall well below my engagement standards. In this case, however, the sparse lines and odd proportions add a layer of melancholy that wouldn't come out if this was drawn in a more consumerist style.