[arethuza]

What I would say you are missing is the amount of business logic there is in a large ERP system. Consider all of the modules of an ERP system:

Finance (GL, Fixed Assets, AR, AP, consolidated reporting)

Product management

Production control

Planning

CRM

HR

Payroll

... a long list of other things

Take all of these features then add an appropriate security model, then add the need to support localized business logic for each country (which you must have to meet local legal requirements) and spice up a bit with business specific customizations.

Do ERP systems have problems? Absolutely. However, like pretty much any developer when I've encountered a lot of systems I've thought "I could design something better than this" - in the case of a large ERP system (mind you, not SAP) I did realise that it was a few orders of magnitude more complex then any small team could really handle.

NB I do think there is a huge opportunity for someone to do for ERPs what Salesforce did for CRM systems.