If it's a specific Mac issue, please state which OS version and display your are using.
I am a Windows only user, so all I can do is to explain 'not in focus'.
What is displayed in the media browsing space is an array of the thumbnails stored in the catalog. They are very small images (240 x 360 pixels) optimized for very fast display of many images in a page.When your image are displayed at a bigger pixels size, the real image is opened and resized to the desired size. Normally, you don't notice the switch between the display of the thumbnail and the real downsized image. However, with heavy psd/tiff file it does take noticeable time. With raw files, a raw conversion is needed, which may require 5 to 10 seconds for a single image.
- try to 'update thumbnail' (right click for contextual menu)
Using OS catalina 10.15.4, w/ 27" monitor. This just came about. The out of focus is immediately noticible when image is in organizer and remains out of focus when moved to editor. I've been using PSE for some years and was debating upgrade from 2019 to 2020. I decided I like 2019 and don't see the need for 2020. I think I will just uninstall and reinstall from PSE disc.