Looking for the same thing myself! It would be great if someone finds a solution to this common question.
My solution was to hard code a converter from the XML file and convert it myself to csv.
I did that in python. Once I convert the XML in csv, I use magmi to load/update the product.
I am still in the experimental phase of my converter but it seems to work until now.
Also included in my "experimental" converter:
1. Find keyword automatically and include them in the meta-keyword section
2. Extract the meta-description from an AI API automatically
3. Adjust prices as needed automatically.
4. Extract the categories and add them automatically.
