The default image size is scretched across the page yet the text is in a margin size of about 540px. The banner image also comes from the thumbnail so using smaller resolution image (.jpg) at 540px becomes incredibly blurry and pixilated on the blog pages.
The setting should be adjusted in index.css to
.article__image max-width: 800px;
margin: auto;
}
Or better yet, provide a setting within the blog page that auto adjust the images to the margin size, ie 540px.