I have my gripes with Google, but from working there, I can definitely give them props for how much they cared about accessibility. It’s in their mission statement, and they take that seriously.
Accessibility at Google suffers in the same way as most UX-related things suffer at Google. Namely, the fact that everything is constantly reinvented from scratch, rather than there being one unified way to do it. As a screen reader user, I can say that in some Google products, there can be instances of what, on the surface, should be exactly the same component, but was apparently developed in multiple different ways. This leads to the constant need to work out how accessible each instance is (and e.g. what keyboard support it has), even though I dealt with the same UI pattern minutes ago.