Westside focuses on what you want it to focus on. You want to target your biceps, look at the volume of rowing work and back work. That also covers lats. Abs are a HUGE part of Westside. Shoulders are used in benching and any type of pressing movement.
The glory of Westside is that it focuses on 3 lifts. Squat, bench, deadlift. The muscles used to train those 3 lifts encompass the entire body. Lats assist in your bench press. If your lats are weak because your biceps are weak, DO SOME BICEPS WORK. If your bench is freezing 6" off your chest, do some extra shoulders work.
You have to be able to identify weaknesses to take full advantage of Westside. But it has proven itself, in the last 25 years, to be the premier routine for adding strength.