No, I don't mean resizing. We've pretty well flogged that dead horse into equine hamburger. This comes before you get to resizing. Many pictures, maybe even most pictures, have too much stuff in them. These can usually be improved by cropping (cutting off unwanted parts). Here are a few examples.
Here's the full, uncropped picture as it came from the camera.
The subject is the vehicles with the mountains as a backdrop. I've cut out most of the distracting branches in the foreground and some of the sky, and removed most of the extraneous stuff behind the trailer. The overall effect is a closer view concentrating on the subject.
Again cutting out some of the periphery to move in for a closer view.
The subject here is the cow and bull, so I've removed the distractions of that guy off in the distance to the left and the bank in the foreground at the bottom.
All that road in the foreground is extraneous, so it goes. Ditto the distracting view to the left of the big tree. With that gone, the tree acts as a frame to lead the viewer's eye into the scene.
Cropping is a simple thing that takes just a few seconds and can improve many pictures.
I agree, there is seldom a photo taken that cannot be improved some, not only by standard cropping but also by changing the width to height ratio to fit the subject. This photo started out as a standard 1.5:1 and was cropped to 2.5:1.