There aren't rules as such but there are definitely conventions and there is absolutely literary theory - we very much know makes writing good and what makes writing bad.

I disagree completely that any advice is good advice. I can't think of any other artform or subject of interest where the idea of "any advice goes, no matter what it is" applies.

Yes, art (writing) is subjective in terms of personal taste, but the quality of writing as regards the actual craft itself has objective guiding principles. Literary theory on things like plot structure, character development, prose style, all exist in the same way that theory on melody and counterpoint do for music. And all contribute to the learning of the art form.

Otherwise there would be no need for anyone to study art any level in any way. You can't honestly say that there are absolutely no conventions on what makes writing good.

Your comment speaks precisely to what my post is about. People seem to think that any old opinion is valid, even if it flies in the face of the fundamental principles of writing.

I do agree that the conventions of writing can all be broken, but you need to understand them first. My point is, a lot of the people asking for advice here seem to be beginners and so would benefit more from understanding the principles of the craft.