Depending upon how we define coordination, I would have to say it can be the essence of management. If by coordination is meant the most effective and efficient use of the resources a manager has to work with, then certainly, this is management's essence.
In order for any organization to succeed, coordination of capital is essential. Borrowing and investing, for example, must be coordinated, to finance expansion, for example, when expansion is likely to be profitable, or to invest capital at times when capital cannot otherwise work for the organization. Cash flow is largely a matter of coordination. The good manager coordinates activities so that cash flow is even or cash is set aside for slumps he or she know are coming.
Coordination of physical assets is imperative as well. Products or services must be produced and provided at particular times and places. This is a matter of coordination. If a manager does not do this, inventory can be a problem, costing space and money to store, or, in the worst cases, perishable inventory, such as heads of lettuce, will sit and rot. Machinery usage must be coordinated so that a factory does not lie fallow.
Coordination of information is a part of a manager's bailiwick, too. What information is distributed or acquired can be thought of as a coordination activity. The timing of a press release is a matter of coordination, for instance. Reports that reach the manager's desk must be prioritized. Gathering information for an IPO is a coordination activity as well.
And of course, a manager simply must coordinate human assets, that is, the people who make up the labor force. Who will be assigned to particular tasks, what hours people will people work, where they will be assigned geographically, what people would comprise the most effective teams are all part of coordination.
Finally, a manager must coordinate all of the facets of the organization itself. The research and development department must be coordinated with the production department. If this is not accomplished, all the great ideas in the world are useless. If the human resources cannot process employment applications during an expansion, hiring becomes impossible. If the marketing department does not know that a new product is being developed, it can hardly get going on a marketing plan. All of this involves coordination.
So, if one defines coordination quite expansively, then yes, it is the essence of management. Certainly, leadership activities are quite important, but a leader who cannot coordinate all of his or her resources is not going to be a successful manager.