This statement is vague because it doesn't provide any specific information about why the movie was good. To make it less vague, you could say:
* "The movie was really good because the acting was amazing."
* "The movie was really good because it had a surprising twist ending."
* "The movie was really good because it was visually stunning."
These examples are more specific and provide more information about why the movie was good, making the statement less vague.