Answer
An effective IT system for a business organization is supposed to help carry out the business processes in efficient and effective manner. A system becomes effective for a business organization if it is designed and developed with the specific requirements of the organization in mind. A custom-build system is always better than a general purpose off-the-shelf system. However, to make such custom-built systems effective, the design and development process should be based on good understanding of the nature of the business and the activities, processes and transactions involved in the business activities. Proper tailoring of the system for the business process requirement needs a thorough understanding of the business processes being automated.
For example, if the need is to design a IT system for an accounting consultancy firm, the development process should be taking input from the actual users of the system and the persons that carry out the daily business activities. A system designed for a marketing agency or an advertisement company shall not be a perfect match for the accounting consultancy firm whose business activities and processes are significantly different from the other two.