Is it essential? If you are a guitar player who dials your tone pot (potentiometer), yes guitar tone caps are essential because the capacitor only contributes to a guitar’s tone the time you lower the tone pot. If you always play the guitar with your tone pot wide open, then the capacitor is not utilized.
The tone potentiometer and capacitor comprise a low-pass filter, so, when you lower the pot, you lose treble, and your tone gets darker. As you substitute capacitors of higher value, you lose more and more highs as you lower the pot.
The most common guitar tone capacitors are denoted by numbers 223, 333 and 473. The higher the number, the darker the sound it will produce when you roll back your potentiometer. Again, if you play with your tone potentiometer (pot) wide open the value of the tone capacitors doesn’t matter.
My advice being a guy with a lot of experience with guitar repair, modification and customization, once you buy a guitar go direct to a guitar technician and have it set up or set it up yourself. Then if you are a player who dials your tone pot (potentiometer), it is an excellent upgrade to change the capacitors. Is is the cheapest upgrade you can do to your guitar.
You will be amazed how the tone changes because the built-in capacitors are usually the cheap ones. Surprisingly, good tone capacitors are not expensive either. Sprague orange drop capacitors are good.
So change that guitar tone caps and welcome to the tone chasers club. Good Day Everyone!