What functionality did it have? In 99% of my apps it had the same functions as the keys except that I had to look at the bar just to reliably change the brightness or volume. There was no way to change the text color on the bar, or the brightness. Meaning that at night in bed with minimum display brightness it was distracting and lit up the room too.
The earlier model I had where the escape key was on the bar as well was even worse as I couldn't hit escape reliably.
There was never a workflow for me where the touchbar would have been of better use rather than keyboard shortcuts. And I couldn't hit the touch keys reliably anyways without looking down at the bar taking my eyes off the display.
To add insult to injury Apple never bothered to improve it. The touchbar in my 2017 MBP was exactly the same as in my 2020 MBP even though the user's wishlists in the forums since 2016 contained many suggestions for improvement, my biggest ones were really just a simple change of text color and dimming it at night. (I had to manually set it to be blank to avoid the annoying bright light at night.)
Apple had 4 years to improve the touch bar until I bought my 2020 MBP but never bothered.
And I did have BTT, I bought a license for it too and thought the touch bar would be the best thing ever at the time. It let me change the text color, but I had to create a custom bar with custom icons and everything. It was alright like that as a customizeable hotkey bar.
But that way it was up to the user to figure out how to make use of the bar with 3rd party software. I already paid for the Mac, why do I have to figure out a way to make included hardware useful and put together my own touchbar layout?
The keyboard of that MBP ended up being so unreliable I ended up switching back to the old 2015 for a while. When I bought the 2020 MBP I accepted the touchbar but realized my license of BTT was no longer supported in the newest version with all the latest features and I lost my touchbar settings from the previous Mac.
Then I just ignored the touch bar and immediately got rid of that thing once the new touchbar-free MBPs came out.
Imagine if the touch bar was the Apple Pencil for iPad, there would never have been a version magnetic charging, and in 2024 instead of releasing a Pencil Pro they'd have just quietly stopped selling the Pencil altogether. That's how Apple treated the touch bar.