I am not sure why there is such a focus on wróg. As is usual with polish courses there is too much emphasis on all the possible cases over structure. I live and work in Poland, but when am I going to need wróg or other words when there is nothing yet for shopping even. It is like learning English by learning all the tenses first. I even ask people at work where I could use words for enemy, friend, judge, lawyer, etc in the office, and they don't know. I cannot even ask for a cup of coffee.
I hear what you are saying too. I've been using Duo for a while now, and am married to a Polish woman. I have a fairly good understanding of grammar and cases but still can't hold a small conversation. It is frustrating. What I have started to do recently is use other resources such as, film, audio books, and other apps to supplement my learning further. Tiny cards is another great app that has been amazing for me so far, and has improved my vocabulary extensively.