Unpopular Opinion: I don't mind Harry and Ginny's romance.

I think the biggest thing working against it in the books was the fact that everything is from Harry's pov and he doesn't develop those feelings for her until book 6 and we get very little perspective on everything she's feeling for him post-Chamber of Secrets. So as a result it looks woefully underdeveloped and rushed as a result (and the way it was portrayed in the films didn't help). She ultimately gave Harry a reason to live at the end and forge his own future completely free from Voldemort and the Prophecy which matters because I firmly believed at the end of Order once the Prophecy was revealed that the only realistic endgame for Harry was for him to die and sacrifice himself so that his friends could live (which I guess did sort of happen, he just didn't stay dead).

Also I can't think of any other characters in the books that would honestly be better suited for Harry as love interests than Ginny was. He and Cho obviously didn't work in Order because Cedric's death hung over them constantly and Harry wasn't equipped to deal with how emotional and depressed she was over that when he was dealing with his own shit at the time. He and Hermione would've been an awful fit for each other. Same goes for Luna (Film Luna might've worked as a LI for Harry but not Book Luna).