I simply don't believe that it generally produces graduates who 'cannot order food in a restaurant'. The phrases required for that are almost always simple. Perhaps you mean that the graduates do not necessarily know certain vocabulary (in the sense of not knowing how to precisely specify a 'rack of lamb' whatever) or the correct register/politeness level for every possibility?

I don’t know what exactly the op meant by delivering a press release, but at least I after a four year high school german course can read newspaper articles in german but would struggle quite a lot to order food (granted, I wasn’t very good at it). In a more grammar heavy language understanding is a lot easier than writing which is a lot easier than speaking.

Is it? I don't know of any person using Duolingo or any other app to perfect their language. Most of them either learn from a uni course or something similar.

Although online, it is praised quite a lot.