The lack of a 'out-of-the box' standard solution makes it harder for client who are looking for a 'plug-and-play' option.
Also, every client's needs may be different and therefore it's hard to start designing a system based on the 'skeleton'. This would lead to many rounds of discussion to conclude on what the client need, and every change is potentially an 'extra' item to build, which could lead to longer time and more cost.
Configuration is not as simple and can take longer time to make basic changes.
The role based access and permissions is useful but not very easy to adopt. Review collected by and hosted on G2.com.