Yes, indeed, what makes art good is largely subjective, but it has to be eye catching to serve its purpose and at least look somewhat professional. I'm actually more put off by bad lettering. If the pencils, inks, colors, and story are flawless, but the lettering doesn't strike the right balance between legibility and dynamism, I won't read it, likely because in too many instances, I can't.
A comic that has dull lettering with dull, typed-in looking fonts may not engage me as a reader very well, but it has an advantage over comics that go too hog wild with fancy fonts and effects or lack clear and distinct caption boxes, word balloons, and such - I can easily read it and make sense of who's saying what.
My opinion on art is influenced by the fact that I work as a letterer as well as a writer. The art has to convey the story and move it along without depending on the words to do all the heavy lifting, for example, drawing somebody smiling and skipping instead of depending on the writer/letterer to make the character explain his/her/hir/their giddy joy.
Also, the art has to leave room in appropriate places for caption boxes, word balloons, thought balloons, et cetera. And if a panel is meant to be read left-top to right-bottom, don't put the character who speaks first in the lower right hand corner.