Everyone got a POV and a reason for their behavior. Choices often made sense and he added some naturalness to some of the plot twists.
There are many examples but one that always stood out to me was during Carly (and Sonny's) battle with AJ over custody. The show was deep into AJ bad and Sonny & Carly good and most script writers got lazy in feeding that narrative by treating AJ as nothing more than either an evil villain or a punching bag. A Mulcahey script would not do that. He'd give AJ a POV and feelings about what was happening just as much as he'd give Sonny & Carly's perspective.
If I hadn't given up on GH over a decade ago, I'd be curious about what they're going to do.