Your site's /blog address displays the page whose slug is blog (type = Page, not a blog post). Create a page (Website > Pages > + Add New) with the slug blog, choose DIY, and add the Blog List module. Its options are Mosaic Grid (on/off) and, under Categories, the category background and text colours. The list shows posts newest first with featured image, author, date and category pills, supports search and category filtering, and loads 10 posts at a time. Link to it from your navigation via Theme: Navigation > Pages to show on footer > Blog (link text is set by Name: Blog) or with a Menu Builder item.