I've been suffering through the touchbar for a few years now and I STILL cannot do this properly. I certainly can't do it without stopping what I am doing and looking at the bar. I tend to either hit mute, Siri, or (if I'm at an unusual angle) I dim the screen. And this happens a LOT of times per day. When I'm on a system with actual buttons it is never, ever an issue.

Yeah. Press on it and start moving and it gives you a volume bar to fine tune the volume, same with brightness. Most other scale-like or timeline controls are similar (versus toggle controls) if they show up in the touch bar for an application.

Protip: you can press a button and train muscle memory, oh - wait.