Not the OP, but I can answer with an objection to COM-style GUIDs myself. Delphi's interfaces are heavily based around COM, and so you need GUIDs, ARC, etc.

But interfaces as a concept don't require the COM backend. If you want your code to be cleanly separated, but don't want to split ownership/management models* (create/free vs ARC), and have no need for an interface and type identity to be managed outside your code and process (ie no COM), then interfaces that are not tied to ARC, and not tied to COM, give the clean code benefit without the baggage.

[*] People work around this by implementing interfaces from a base class with no-op AddRef/Release methods. But this kinda shows the problem: why is that necessary?

I work with Oxygene which is another modern Pascal -- quite a few new Pascals have popped up recently, I get the sense there's a real desire for something new! Our interfaces can be 'clean' and we support soft interfaces, too.