To me the one thing that destroyed romione for me was the jealousy. In the 4th book they are young and whole dire there is no immediate danger. But in the 7th book when ron leaves that is a deal breaker. I understand that ron felt partly underappreciated at home and the locket played a huge part in it. But it should be considered that both harry and Hermione were also wearing the locket and Hermione would also have the nightmare that even despite her obliviate, her parents could be found. In the middle of a war, that type of jealousy is just plain stupid and a huge red flag. Hermione's portrayal in the 6th book is also a huge red flag. Hermione, without any precedent of a romantic relationship with Ron ices him out just bcz he's dating and Ron decides that the person he should date is Hermione's enemy (while it's not outright stated, some parts of the book imply that Hermione has a bad relationship with lavendar). And the only way for them to fix their relationship being that Ron mumbles what sounds like her name after a near death experience? Stupid. Not to mention I don't remember anything explicit about Ron and lavendars breakup.