exercise reps * weight lifted = (mass + strength) / years lifting
Compound movements allow for the most weight to be moved giving you the biggest bang for your time invested.
My 2 Cents from personal experience and every person I have ever seen in the gym for years on end:
Your body has a blue print that it wants to adhere to thanks to millions of years of evolution and changing that blue print is difficult at best even with drugs.
This makes me think that isolation work and pump work are near worthless when mass/strength is concerned outside of maintaining a balance to keep you healthy which in turn means more weight moved.
"but, but, but all those top level body builders and physique models do this and that"
- Enhanced means that anything they do works to a point and
- those huge body builders are spending several hours a day in the gym.
As a natural one doesn't apply and two isn't an option.