Firstly i wanna say that i really don’t mean to offend anyone, this is my opinion and you may agree or disagree with it. 
I would say, really bad grammar and spelling, now i know not everyone’s first language is english and i totally understand that! But if it came to the point where it’s unreadable then that’s a problem to me:(
A lot of directing mistakes.
Bland dialogues.
Long narrations describing the characters personality, i prefer the author to show not tell! 
A rushed one, like a sudden ending where there’s still a lot of stuff unsolved and doesn’t make sense!
If it happened once, firstly i would contact the author nicely and tell them that, and most probably continue reading, i won’t judge on the first mistake! But if it’s getting too consistent, then i would stop reading ngl.
Long intros, especially if the previous chapter ended in a cliffhanger, as you said irrelevant dialogues and a predictable scene, for example the club scene where the MC is in danger then the LI will save her.
Advanced directing and an interesting plot really catches my eyes! I would just say oh lala this author knows their way into writing a story yk? sjkdhjs 
A unique plot, interesting characters with remarkable personalities and that i can relate to, funny jokes/memes, mini games! 
I actually just posted a thread with tips for authors!! 
Here’s the link!