I noticed in alpha.1 – 11/27/2017 that you “added alt tags.” However, it doesn’t appear that this is working correctly.
I have this on a staging site: https://staging-brianjackson.kinsta.com/blog/
You can see for example on that first blog post, the featured image shows up. The alt tag shows as “I’m Joining the WordPress Team at Kinsta”
However, in the media library I have clearly set the alt tag on this image to “Kinsta.”
I also tried throwing GP 2 on a site that didn’t have GP before and experienced the same issue. It appears that GP is pulling the title of the blog post for the alt tags, which is not ideal. This also occurs on the featured image inside the blog post as well.