Steady State Error: why we use a negative feedback rather than a single gain to reduce the error?
It's the stability that's impractical in the real world.

Mathematically, numbers look very stable, and yes, of course we can tweak a coefficient here and get the answer we want.

In the real world, complicated amplifier components are very temperature sensitive, and vary from batch to batch. 

Simple feedback components, a pair a resistors for example, are orders of magnitude more stable and easier to adjust. That's why the world builds amplifiers with 'too much' gain, then knocks it back down with negative feedback.