With RFC modules, no generic types are allowed

What causes this issue?

You attempted to assign a generic type to a parameter of a remotely
called function module. This is not supported.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

You must assign either a reference field or a reference structure to
each function parameter.

Error message extract from SAP system. Copyright SAP SE.