Look:

Curls, quad extensions, lateral raises, and pull downs are all great exercises but are not going to really change your muscle building game as much as you are hoping.

Compound exercises are the staple to a great physique!

They help build physiological symmetry and proportionality, burn calories like crazy, and help build muscle in areas that you’ve not even heard of.

Compound exercises are also great for improving testosterone and HGH production, which are hormones linked with muscle growth.

Furthermore, they are great for building strength, which will help you out with your other exercises.

For example…

By improving your pull-ups you are essentially improving your pulling strength and thus will be able to increase the lifting load on your curls;

Improving your dips (chest or triceps) improves your pushing mobility thus helps you enhance your bench, push-ups, and other push-related-exercises.

In other words:

Compound exercises have a trickle-down effect where they don’t just improve muscle development themselves but also elevate the impact that other exercises poses on growth.

Summary:

Compound exercises are fundamental for muscle growth. They help build a more symmetrical physique and are shown to improve testosterone and HGH production.