I always tell people: 1) Food 2) Training. In that order. You have to take in more calories than you burn. You have to have protein AND carbs to build. A pro BB (can't remember who just now) once said, great bodies take years not months to build. So, change is incremental. Another factor is genetics. Obviously, you are noticing that. In any case, the best way is with compound exercises where you can, ones that use more than an isolated muscle group.
For delts, a pro once told me to focus on rear delts and it was great advice. I do rear-delt flies 1 time a week with my back workout. The results speak for themselves. They have really added mass. As to front delts, you are gonna build them with incline presses, even front militaries (rear militaries are rough on the shoulder joint). And side delts - flies. For me, I use dumbbells and do one side at a time, standing, using my opposite arm to grab something and support my body. It lets me go a little heavier. I also have to say that good lat work will push your shoulders out to the side, so do lats as well. I usually do 4 or 5 sets, pyramided, with the last set at 5 reps. Lastly, don't ignore shrugs for your traps. the shoulder areas is delts AND traps. If you want, do upright rowing for front delts and traps together.
Triceps are pretty simple. Really you have a lot of variations, but only 2 basic moves: overhand and underhand. So you can do pushdowns/dips/reversegrip bench/single side underhand pulls (high or low). It's good to do your tris on chest day, as any pressing (flat/incline/decline/dips) heavily engage your tris in compound moves. So, after the chest workout, and if you do shoulders same day, then go to tris. Do 2 exerises: a push and a pull. Me, I like pressdowns because skull crushers are nasty on my elbows and wrists, then I finish with underhand pulls, one arm at a time. In both, I usually do 4 or 5 sets of 8 reps, increasing the weight.