If you're asking for a 10/10 manga with shitty ass art the first one that comes to mind is 'One Outs' , it has phenomenal plot, god tier characters, the MC is really good and it has some of the best twists and a very satisfying ending. The art however is dog shit, it's like someone drew it as a rough draft and posted it, still I'd highly recommend it.
Another 10/10 is 'Onani Master Kurosawa' (Masturbator Master Kurosawa - wierd name I know) but yeah this one isn't for everyone because it gets super edgy at times but if you really want to read a one of a kind manga then this is the one. The art is pretty shit but that's to be expected since it was one of the artist's first works, now he's a lot better.
As long as your story is engaging and gets the reader invested I don't think the art really matters, of course for it to be a popular work the art has to be decent but as far as fans are considered, if your work connects with people then no matter how few, someone will be thankful that you decided to create this work.
Of course not everyone shares the same sentiments as I do seeing as some people refuse to read Jojo's because of it's supposed 'hideous art' even though it is arguably one of the greatest manga of all time, not just because of it's plot but because of the impact it has on the modern anime and manga culture, I think that in itself warrants it a read.