Did you know that canned, diced tomatoes are treated so they actually hold their shape longer? I know this might seem obvious, but diced tomatoes aren’t just….well…diced tomatoes. They’re actually diced tomatoes with calcium chloride and citric acid added to them to help them keep their shape. So when you buy a can of diced tomatoes and try to cook a smooth marinara sauce with it? Well, it just doesn’t work.
On another note, I am not crazy about running diced (or whole for that matter) tomatoes through a blender to make them into “crushed” tomatoes. When you puree them in a blender you’re whipping in a lot of air and changing the texture. Same applies to a stick blender. If I were to ever break down tomatoes for a sauce I’d use an old school ricer, or be really rustic and use my hands to break them apart.