Tone stacks contour the sound in a certain way that is unique to that tone stack. While you have a lot of adjustments with tone controls, the range of those controls is in the design and component values in the tone stack.
For decades, there have been two competing sounds that are slyly referred to as "American Sound" and "British Sound." One of the main differences in these approaches to amp sound is the tone stack.
Some amps let you bypass the tone stack. It is then that you really hear the rest of the amp's design.