Deadlifts are great. But people need to know what "heavy" really means. For a deadlift that means at least two times your bodyweight. Many people in the gym just don't try hard enough.
Also as to what is a heavy amount of what is a light amount - its irrelevant to an individual. You should lift the an amount that pushes you beyond what your comfortable with, but not so much that your risk injury.
Heavy lifting and trying hard is important, like you say, but it's a relative thing to experience, genetics, age, etc. I've seen grannies pull 1.1x bodyweight and I'd say they were lifting "heavy".