I agree with Canadian John. If you don't try, you will never know.
For me, I've tried injecting and it imparted a nice flavor and moisture. However, I choose not to inject because my best briskets have come from getting better at evaluating and choosing the right brisket to purchase (quality of protein as CJ said).
Learning how to pick a nicely marbled and uniformly shaped brisket has been the primary factor in achieving my best brisket cooks. Therefore, the rub (SPG for me) and sauce (sometimes) are all I need for extra flavor.
But give it a shot so you can learn what your preferences are. Nothing beats experimenting with brisket imo.