Lost almost completely is the thought and mystery and wonder Scooby Doo usually has.
In its place is a terrible romance comedy with the thinnest message (people can be friends without romance).
This is a terrible script, even for a cookie-cutter teen romance, and the writers demonstrate they likely: never watched an episode of Scooby Doo; never read Nancy Drew, Sherlock Holmes, or anything of that ilk; have little understanding of humor or human emotion.
Beyond the script, the characters are shallow, vapid and self-interested (no longer the flawed comic heroes of the source materials). Perhaps you think this earns 2 stars for those parents who need their children occupied at any cost, but consider that cost: their growing minds filled with some of the worst role models available.