Bodybuilding = Legs + Back. Everything else is commentary.
I intensely train my back. I try to hit the upper, lower, outer (lats, teres major) and mid-back muscles. Lots of variety, big menu of exercises for each.
New favorite upper back / rear delt exercise: face pulls, specifically seated, pully / cable face pulls with rope.
Not all gyms have the machines / equipment for it, but I love one arm movements: one-arm lat pulldowns; one-arm 45 degree pulldowns, one arm pully / cable rows, dumbbell rows, etc. One arm movements mean that way my dominant (right) side doesn't do more than its half of the work. Also, with many one-arm movements I have a better range of motion.
Agree that the amount of weight isn't necessarily all that important. Like others here I often improve my form and get that sweet contraction by lowering the weight, and in that way get better results.
For muscle hypertrophy, you don't necessarily need to train heavy. You need to train hard, to failure.
Always looking for new ideas of different exercises, and alternate ways to perform those exercises, including different body positions (seated, standing, body leaning into / away from weight) different handles, grips (rope, V-bar, easy curl bar, straight bar, etc + wide grip, narrow grip, shoulder width grip, etc).
I like watching YouTube vids of bodybuilders training back (Jus Compton has a couple of good ones). Also watch and talk with other guys I respect at the gym, always looking to share, trade information.