Changing volume is definitely one of those use cases where the physical function keys were much better IMO - It's one physical button press rather than touch the button, look down at the slider, and try to drag it into the right position.

I also use my laptop in a dock about 50% of the time, so end up just using the on-screen volume adjustment and keyboard shortcuts anyway... If Apple really believed in the concept they would have put the touchbar into their keyboards too.