Every ERP implementation, however well-scoped, leaves gaps between the standard configuration and how a specific business actually operates. A one-off approval process, a customer-specific workflow, an operational report that doesn't map cleanly to a standard object. These are normal, not a sign the implementation went wrong.
The question is what fills that gap. Left unaddressed, it gets filled by manual workarounds: someone exporting data, applying logic in a spreadsheet, and re-entering results by hand. That works until it doesn't, usually right when volume increases or the person who built the workaround leaves.
Oracle APEX is a practical answer to this specific problem. Because it sits close to the underlying data model, it's well suited to building small, purpose-built applications, such as an approval portal, a data validation tool, an operational dashboard, without the overhead of a full custom development project or the fragility of another disconnected spreadsheet.
The organizations that use this well treat APEX extensions as part of the enterprise application landscape, not a side project: version-controlled, documented, and reviewed as part of the same quarterly update process as the core ERP. Treated any other way, the extension becomes exactly the kind of undocumented workaround it was built to replace.
The goal isn't to avoid gaps between ERP and operations; there will always be some. The goal is to close them with something maintainable, instead of something held together by one person's memory.