I hear many people say they feel intimidated or overwhelmed by the quantity of information painting from life presents. It would be helpful, I think, to have some guidelines. What needs to be included in a painting and what can be let go? What is essential, we are asking, and what is optional?
Let's try to zero in on the fundamental aspects of the alleyway we visited today. We started by looking at the space as a shoebox. As such, the most significant visual features were the sides and top and bottom of the box, or the planes that defined the space.
This way of seeing recognizes the planes as more important than the individual fences, garages, bushes and dumpsters each plane comprises. It is essential to make apparent that there are vertical and horizontal planes first, and then to make some reference to the more specific, smaller components within each plane. If the viewer were unable to identify just what those components were, or exactly how many there were, it would still be possible to feel the basic structure of the scene. Most of the specific information can be released. That hypothetical viewer will do the work of making it all meaningful.
Once you have discovered that there are boxes full of information that do not need to be named, it is useful to shift into abstract vision. All those recycle bins and garage doors can be sufficiently described by just making some rectangles within the larger shapes that represent the big planes. Give the viewer some credit. They will recognize those rectangles as "alleyway stuff", and that's good enough. It is not your job to make sure the viewer can tell exactly what they're looking at.