Weird! I checked out the new Macbook Pro at an Apple Store and there was an escape key on the touch bar, at the left end where one might expect it. It seemed to work in Terminal >Emacs where it served as the M- modifier. It also worked in open file dialogs in Preview and TextEdit. I assume it would work just fine in other file dialogs as well.
I have no idea of where your escape key went. Did you play with the configuration? I gather the touch bar has a lot of configuration options, so you might have turned off the escape key when you were setting up your environment.