To export your Google Maps starred locations:
Go to Google Bookmarks: https://www.google.com/bookmarks/
On the bottom left, click "Export bookmarks": https://www.google.com/bookmarks/bookmarks.html?hl=en
After downloading the html file, run this script on it to generate a KML.
It's hacky and doesn't work on all of them, but it kinda works.
Unfortunately, impossible to get the GPS coordinates for anything else than the locations with stars. Personally, I used exportgooglemaps.com; this tool takes the CSV and JSON from Google Takeout and create new files. You get the Place ID, GPS coordinates, and a few more columns, but that's what I needed the most. Not sure why Google doesn't give better files...