Just to be clear on this
Train the lift to improve the lift - bench press to improve the bench, squat to improve the squat, etc.
Train the muscles involved as prime movers in that lift, to help increase the lift - pecs/shoulders/triceps for benching, quads for squatting, etc.
Train the supportive structures to provide a better base for the lift - train the upperback, calves, hamstrings, biceps, etc.
Having a great supportive base will NOT increase the lift, i.e. having strong rear delts will not increase your bench. That is done with the first two points. Yes, it's important to have a strong supportive base, but it's a small component compared to the first two things.
Your goal should be to get bigger and stronger all over. However the reason for articles like I have written and Mike Israetel wrote is because sometimes people become too focused on the wrong things to increase a lift, then wonder why progress isn't as optimal as they would like. Lat pulldowns aren't the reason your bench is stuck, and leg curls aren't the answer to a bigger squat.