While HP:DH does have a "summary" vibe, going back to all the old places and seeing all the old characters' plots wrapped up nicely, I do think she needed SOME new material in there. She needed to create new tension, she needed new suspense; simply wrapping up things she'd already devised wouldn't have been fresh enough for her, or for us, I think.
If I had to change just two things about DH, I think I'd remove the epilogue (it could just be an online essay, there's no need to put a second bow on top of the present, you know?) and I'd remove wand lore. The idea that your wand changes allegiance whenever someone bests you in any way, physical or magical? Come on, that is borderline plot manipulation. Now, Harry wins the fight at the end because Voldemort's wand knew that Harry's hands pulled some wands out of Draco's hand, who in turn disarmed a Dumbledore who wasn't trying to not be disarmed? I mean, ugh, wand lore was a sort of hand-wavey MEH aspect, IMO.
I think Book 6 and Book 3 are the pinnacles...they don't feature battles with Lord Voldemort, they're nicely self-contained, they have fantastic endings, I'm getting chills thinking of them.
Why was the book centered around a children’s story that we didn’t hear about until book 7? Why were the deathly hollows items not mentioned at all throughout the entire rest of the series? Why do we not find out until the last book that the invisibility cloak should have faded a long time ago? That last point especially irritates me because it just smells like lazy writing.
I love Harry Potter. I have read the series many many times. I sincerely wish I had never read the last book. It felt rushed, unplanned, and almost desperate.
There is a fluid cohesion between books 1-6 that completely disappears in book 7.