The Featured Image is very important when it comes to readers finding the article on the site.
The image size for the Featured Image is 750px x 450px. Please make sure the image is composed well.
Using the Alt Text on images in your articles, and especially the Featured Image will go a long way in helping others discover your article.
Your Featured Image should include the Alt Text that includes the title of the article, and the Description, which can be the first paragraph of your article.