Plans are useless. Planning is essential.
Let me tell you a story about one of my teams that fell apart. And all it would have required was some amount of planning and focus to give people perspective and purpose.
A while ago I took over a team, that had gone through a rough phase of uncertainty. At this point, the single biggest thing the team was lacking, was a sense of value that their work created.
They didn't even see the value in having sprints anymore, so to simplify and focus, we dropped sprints altogether in favor of adopting a flexible Kanban process.
This freedom caused more harm, however, because the product owner team took this freedom to mean, there was no need for planning anymore. That they could just throw stories over the fence, when resources were available. I use the word resources here intentionally, because that what people feel like in these situations: resources to be tapped when a 'resource manager' – the PO – feels, it needs utilizing. No outlook on what's to come, no clarity, certainty or vision.
As the product team continued to work off their high-level roadmaps and visual mock-ups, engineers grew more and more frustrated and the team started to fall apart. That management pushed competing projects onto the team didn't help either.
With no vision, no clarity of where things are going, people left, changed teams or fell into a stupor.
And all it would have required was some amount of planning and focus. Giving people perspective and purpose.
Of course nobody expects plans to be set in stone – we're working agile after all. But to keep flexible and to change a plan, the first, absolutely essential thing you need, is a plan.