Poor acting (some of the worst I've ever seen), plot (one-dimensional, predictable, and uninteresting), and overall message (preachy and definitely not empowering). Dated, conceptually flawed, unfunny. There's a speech around 1:08 which epitomises everything wrong with this movie. Women do not need a man to tell them what they need, and the message of the speech is frankly incorrect: women should be able to choose for themselves whether they want to hook up, or date; and some women DO want NSA. The movie is incorrect: dating does happen.
The concept of the hookup app is also flawed: in the real world women (in general) are not desperate enough, nor men (in general) seedy enough, for such an app to take off. The message of the movie is not to use apps, yet this is bizarre also: an increasing number of long-term relationships are built off matches made online. It decreases the chances of a great match if you limit your dating pool, and there's no reason why anyone should rule out apps based off an arbitrary ideal. Also, people were having a lot more sex in the 50s and 60s than this movie makes out. Some studies actually suggest they were having MORE sex than young people today.
The comedy in the movie is very poor, particularly in delivery. I get that it's an American teen movie, but it's lacking wit or any kind of depth to the jokes.
All characters are one-dimensional and lacking depth. All follow established, over-used cliches.