It's a bit odd to mix military terms and design but I recently came across the term "commander's intent" and felt it was a good articulation of how to build great client-designer communications.
Instead of giving a detailed, step-by-step instructions, Commander’s Intent involves giving a description and definition of what a successful mission will look like, then turning over the specifics to the soldiers in the field. The idea being that if the overall goals are understood at a high-level, teams are empowered to make quick decisions and seek better outcomes than if they are just routinely following instructions.
While design hardly requires the same split second decision-making, a similar thought-process can apply. For us as designers, it's often much more helpful to hear your overarching concerns (it feels too busy) rather than specific instructions (move this line left by 10 pixels).
While it seems easy enough on the surfect, with any design change, there's inevitably a domino effect to the overall design. When we move the line over 10 pixels, it is now crowding the sidebar but was that your intent? Or did you want to maintain the spacing and decrease the sidebar by 10 pixels as well? When we make the sidebar smaller the thumbnails images decrease and now the header image looks unbalanced...and so on.
When we don't understand why we're making a change, it can often mean we're either making assumptions that snowball or constantly needing input and feedback.
If we understand that the overall goal is to make the page have more whitespace, we can use our problem solving skills to come up with several options that work. You can even still give a specific solution (like moving the line 10 pixels) that you think will work. However when we have your overall vision in mind, it's much easier for us to make a solution that works.