unsatisfying
Leaving you feeling disappointed or like something important is missing.
Unsatisfying means leaving you disappointed or unfulfilled, like something didn't live up to what you hoped for or needed. When a movie has an unsatisfying ending, you finish watching but feel let down because important questions weren't answered or the conclusion felt rushed. When a meal is unsatisfying, you might still feel hungry afterward, or it just didn't taste as good as you expected.
The word captures that frustrated feeling when something is technically complete but doesn't feel actually complete. You might find a book's conclusion unsatisfying even though the author wrapped up the plot, because the characters' choices didn't make sense. A game can be unsatisfying if winning feels too easy or the challenge disappears too quickly.
Notice the difference between unsatisfying and simply bad. Something unsatisfying often has potential or starts well but fails to deliver what it promised. Your friend's explanation of how a magic trick works might be unsatisfying not because it's wrong, but because it leaves out the most interesting parts. When you work hard on a project but it turns out unsatisfying, you can tell something important is missing, even if you can't immediately identify what. That restless, incomplete feeling is what makes something unsatisfying.