Don't think we are disagreeing. It used to be that the large SI's would run something like an XML consulting practice alongside say a SAP Practice, a Systems Security Practice, a Software Testing practice etc little centres of consulting excellence with the company, much like a large law firm would have Property, Employment, Commercial and Family Divisions. Back then they had more of a shot at resourcing a complex project because they would have alot of the expertise in house but this was before global outsourcing and the commoditisation of IT skills, when IBM was the worlds largest company and the likes of Logica were in the FTSE100. My guess is that consulting firms had to specialise in order to be able to justify billing above commoditised rates - this puts more onus on the client to be able to recognise that they need that type of consultant in the first place.

Things would be alot better if companies had incentivised universities to teach things like Systems Theory and the History of Computing instead of Java. With the marginalisation of older IT workers we are approaching a time when it will be common to encounter enterprises whose resources have never known anything other than OO/RDBMS development so things like MarkLogic will continue to be seen as weird. Back in the day  the diversity of expertise under one roof meant there was a counterbalance to a clients tendency to self medicate or be to prescriptive about a solution. Whereas today if you go to a consulting firm like Thoughtworks the type of solution you will likely emerge with will be quite narrowly constrained.