Holding most people back on BACK growth
I think the main reason most people have such shitty back development can be found in every gym on a daily basis. People are using way too much weight on nearly every back exercise.
Lat Pull Downs - where are the pull ups people? Ditch the pull downs for pull ups OR if you insist on doing pulldowns stop rocking back and forth using momentum. I see guys using the stack (or close to it) that weigh 195lb soaking wet. Makes no sense.
Barbell Rows - The rare occasion you even see guys do them in the gym, you end up watching some sort of hamstring, RDL, row combination. How many more muscles can you incorporate in the lift for Christ sake!? Drop the weight in HALF and actually feel a contraction before you try to lift 3 or 4 plates a side.