Why do you idiots always try to make this argument as though I'm recommending people NOT squat and deadlift and only do "curls and kick backs"? What the fuck is that?
The guy who will be bigger and stronger than both of those two is going to be one that trains EVERYTHING.
How about you "show me" either of those people that exist in real life?
Yeah you could argue that... if you had any evidence of it whatsoever, which you don't. How about I argue that the bigger you get, the more invisible fairies sprinkle dust on your biceps that makes them grow more easily once you can squat a subjective amount of weight?
Why do you think "mastering" the squat and deadlift makes you suddenly strong at everything? Why do you think shrugs are supposed to make your shoulders bigger?
Unless by "mastering" you meant... you can lift impressive poundages because you ate right and trained all your muscles to handle it... In which case NO FUCKING SHIT everything got stronger because you TRAINED IT. How about you show me someone who has "mastered" squats, who has only ever squatted and done nothing else? (hint: powerlifters who are any good at their sport at all train EVERYTHING)
Eating is going to get you bigger. Doing squats and deadlifts along with that is going to make your thighs, glutes, and back bigger.
And again with the ridiculous examples? The world of strength training is not separated into two camps where in one you do "squats and deadlifts and just gain weight", and in the other one you only do "kick backs and curls while worrying about whether your real delts pop".
There is this middle ground where you train everything evenly so that you can be big, strong, proportionate, and not get injured because of imbalances and weaknesses.