I don't see how entertainment is foolish or certain hobbies are a waste of time. Entertainment is a good way to wind down, and have fun. Then using the knowledge and experience you gain from reading a book, or watching a movie, or playing a game is a good way to find common interests with others. Having hobbies is a good way to enjoy your life and to relate with other people who share your interests. In general I think it would rather difficult to do something that is a complete waste of time, as in something which you can't learn anything from or gain any experience for the future. You're pretty much always learning no matter what you do.
There's nothing wrong with having a bit of fun. Really personally I would not be stressed out how you are wasting time by having certain hobbies, there is always something positive to gain I think. Just do whatever you like and try to keep your chin up!