There's an accessibility mode you can enable which provides keyboard and menu navigation, as well as audio cues. It's basically an alternative interface for interacting with the data layer.

I actually think this is a better approach to accessibility in web applications than trying to hang all of HTML+CSS+ARIA on the DOM. Check out Accessibility Object Model (AOM) for one spec proposal around this idea.

While not directly related to your question, Google docs' switch to canvas broke my custom dark theme which I'd been maintaining for years, and several others were also using. This had been the main draw for me switching to Google docs in the first place and they took it away. I'd argue this is much less accessible as I can't use the product at night. Ironically, I feel like I've experienced more bugs after the switch than before