When I moved to the Storygraph I used a Goodreads export. If I remember correctly, I just had to delete some extraneous columns and (maybe?) re-arrange some others. It was certainly worth doing over recreating the data from scratch, and I didn't have 4000 books!

I agree that Goodreads could do better with recommendations, but I keep wishing that Netflix's recommendations would come up to the Goodreads standard.