Architectural illustrations and 3D renderings are the same thing as composition. Despite rumours to the contrary, there's no imperative difference. They both boil down to what you put where. We make decisions then we place 3D geometry in one place or another on our screen.
Composition and design are ultimately what an architectural illustration and 3D rendering is about. Many 3D artists feel intimidated by design, that it's more than they want to deal with. They push it into the back-burner and hope that somehow it will take care of itself. However, the fact is that design can be demystified - and it must be, since consistently successful results come no other way.
Mountain climbing seems to mirror the act of creating 3D art. Does anyone just forgo planning and "hit the road" to reach the peak? Obviously, not if you intent to see the view from the top, and not if you plan to get there again. Happy accidents seldom happen when climbing to great heights. That requires understanding, planning and practice.
Even with a plan, success is never guaranteed. It just improves the chances. Good composition requires a well-developed sense of design. How do you require good design? You study, observe, and ask questions. In the process, you learn to see critically. And you render - a lot, while consciously applying the concepts you've discovered.
We're all aware that there's much about art that is intuitive. But few realise how much of art is logical and reasonable. It can be understood. And, once understood and absorbed, eventually it becomes second nature. Anyone who sets out with serious intent can master design.