True DRP is a very hard problem to model.
Firstly you have to set what your distribution strategy is (do I optimise for distance, delivery time, total fulfilment time... etc.), you also have to model your operational setup (are you a network warehousing system, a hub and spoke system, a node-satellite system). Then you have to define fulfilment rules: which warehouse to look in first, do I pick partial quantity or not, what happens if that warehouse has an order coming in, do I consider it or not?

As you can see it is an engine of its own, and attempting to write a functionality without considering all these values might mean we have a functionality that doesn't cater for most real life scenarios which means it won't be used.

I thought I'd shed some light on the complexity here, but I think we really lack a proper DRP function in D365SCM.