I greatly respect when an app developer takes the care to design their app to follow their OS Human Interface Guidelines. Apps like Apollo (and wefwef/Voyager for Lemmy) for example rose to popularity partly due to looking and feeling like native iOS apps
It seems that many popular mobile apps have their own design language. Though may be pretty in their own right, I like consistency between my apps
To give an example, one of my favorite is Liftin (iOS). The dev did a great job making it feel like an extension of the native Apple Workouts app
Ivory from the Tweetbot devs, although is not purely Apple-y, it feels like it belongs in the platform while also adding something of their own.