The irony is that real FSI language courses generally produce graduates who can read the newspaper and deliver a press release but cannot order food in a restaurant or explain to the delivery driver how to reach their apartment.
I never met an FSI graduate who felt their language training was great. I met many who felt it wasn't, and many who had to effectively relearn the language when they arrived in country.
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.
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?