Pressure, extraction duration, temperature, grind uniformity, and tamping are crucial in achieving flawless espresso shots. You won't like your final espresso drink if these are flawed. Instead, what you'll get are relatively flavorless espresso shots.
Each element must be adjusted precisely if you want to make espresso shots anyone would die for. Of course, naturally, you have no influence over all of these factors. However, the objective is to pursue perfection and get the best results.