There were two solutions to this that the market could have pursued. They could have improved the interfaces so that applications could integrate effectively until this wasn't a problem or they could build all the applications in the same environment such that, because they are all modules of the same application, they don't need to interface as separate products. Some solution providers chose to go down the latter route and they have become very successful. Integration and communication technology has improved exponentially in the last five years. Middleware', the interface software and expertise sitting between best of breed applications, is now very big business.
System integration is no longer a problem.
The problem of integration that they set out to solve eight years ago has gone away making their concept redundant. Advances in technology have removed the original problem.