How to make outbuilding remains look aesthetically pleasing
Why not make it a bit of a patio? Put a wooden latticework screen in front of the remaining walls, a wooden deck over the concrete floor (unless the floor can be cleaned up sufficiently), and a pergola over the top.

You could have vines climb the lattice and over the top, based in containers if the ground is not accessible.

Add a grill, a few chairs and you have a sylvan retreat.