You can solve that problem by going into keyboard settings and changing the "Touch Bar shows" setting to "Expanded Control Strip". Or "F1, F2, etc. keys" if you prefer. Whichever one you set, holding down the "fn" key will temporarily toggle to the other one.
You still don't get the same feel as physical keys, but no Siri, no sliders to adjust volume or brightness, no stuff shifting around as you switch apps.
You can do that, but keys on glass are still in every way inferior to physical keys.
I didn't claim that this solves all issues someone might have with the touchbar. Just the specific "I keep triggering Siri" issue.
Yes, it's just annoying that the best workaround involves replacing the touch bar functionality with an inferior replica of the physical keys it replaced.
I don't understand how this didn't come up in usability testing
You can disable the siri in Touch Bar and configure it to have the buttons you want. We do that to every new laptop we give our team, it's great.