Unfortunately you can't remove Siri completely. That's an option I miss in this OS.
But you can ignore the bitch. Above you see my settings. Just turn off whatever you see: show on menubar and set "Ask Siri" to off.
On the touchbar Siri is placed on a really annoying position. At least for me - Siri started every time my fingers touched the bar by accident.
Siri is not a service. It's a pestilence.
Now I hope that Siri is silenced at last - but I would prefer if Apple asked permission before installing this crap-ware.