Custom off the Shelf (COTS) CRM or ERP solutions, typically, require extensive customization prior to and then after their introduction into any enterprise. This is a fundamental consequence of the nature of COTS solutions, specifically that they are more off the shelf than they are custom, and the process of making it your own, so to speak, is time consuming and costly.
Built for the masses, COTS solutions incorporate known, baseline needs as opposed to the unknown, unique intangibles that each enterprise requires. Moreover, once implemented it is the COTS provider in control of the development and growth of the platform, not you. This means that as your needs change the solution does not adjust along with these new needs, leading to productivity issues, lost revenue and customer-impacting realities.