First of all not all powerlifting programs have "very little accessory work"... Westside barbell training is 80% accessory work for example.
By balanced I assume you mean having all muscles with good strength rations. The answer is maybe.
A minimalist approach (only a few big lifts) work if you have no muscle dominances, in other words if all your muscles are already in balance and if you levers allow you to load all your muscles optimally. But that is RARELLY the case... in most people one muscle will always tend to take over, leaving under stimulated.
So I will say that for a balanced physique most people will need to use accessory work, mostly to target their weaknesses.