Images quality

Check the WordPress settings, it can reduce the requested image size, my plugin uses the original image.

I have disabled WordPress settings, it does not crop images. The size of my image is 1200 x 980px. As far as I understand they should be much larger?

I had the same issue.
Starting with WordPress 5.3 a resizing of the images was introduced.

Introducing handling of big images in WordPress 5.3

I my case I had to delete “-scaled” in the filename of the chosen panorama image to use the full-size picture.