Definite article

(1) The nurses in this hospital are nice.

(2) Nurses in this hospital are nice.

(3) I love nurses in this hospital.

(4) I love the nurses in this hospital.

As I know that (1) and (2) have the same meaning, can use either.

But I don't understand why I can't use (3), only (4) are correct to use.

Could you please help me explain the reason?