I need to counter the argument that you can not write complex systems without OOP. SAPs ERP system is arguably one of the biggest, if not the biggest software

I need to counter the argument that you can not write complex systems without OOP. SAPs ERP system is arguably one of the biggest, if not the biggest software system on the planet. It is written in ABAP and ABAP is a procedural/imperative language. SAP is open source and the code is fairly easy to read. Reusability of functions an procedures provided is fairly easy and groundwork for every developer working with SAP to modifiy, enhance functionality or writing add ons. Or more specifically it was. ABAP got OOP extensions about 10 years ago and since then the code became more and more inflexible and less maintainable for people other than the original authors. But maybe the main point about ABAP is that despite its procedural nature it allows data centric programming. You take a line of data, transform this line and return the transformed line. No need for abstractions, inheritances and complex design patterns, concerns with mutability etc. Just plain and simple solving domain problems instead of problems caused from abstraction.