The main disadvantage of shelf software is indirectly also its most significant advantage. Because shelf software is designed for and paid for by the masses, it’s usually quite cheap compared to custom software. On the other hand, the generalization is also its most considerable disadvantage because it removes the need for any specific details that you might require.
Many providers of shelf software are beginning to realize this niche and creating hybrid shell software. You get to pay for the base software, and then pay an additional fee for every customization that you’d like to add to the existing software.