“But from the perspective of a coherent story in a coherent world, ignoring the success in terms of sales, it was cobbled together without a plan, and it shows. It wasn’t until maybe order of the phoenix that she had a plan for how the story would end, and she had to do a lot of hand waving to make it happen.”

“But she wasn’t a good writer. She was mid tier at best. So the eventual success of the series got beyond her abilities. While the last book was much better overall than the first few, it still relied on shoddy world building”

Excellent explanation. The first HP book is excellent. It really sucks you in. After book 4, the quality declines and they become slogs to get through.