What is a blanket statement?
It’s a general statement. Also, “blanket statements” are usually used to tell people what they should or shouldn’t do, but the phrase is often used in jest to ridicule those who espouse them.
The phrase refers to a generalization that is too broadly applied- for example, that no one can ever be happy if he/she doesn’t have love. The implication is that the person making the blanket statement has not made any effort to find out what satisfies an individual person and applies this same solution (in this example- love) to everyone.