This should now be a lot better. It's difficult for me to say how much because there are still some outstanding issues that affect screen readers (and I am a screen reader user), but these won't apply to most users, even if they have accessibility enabled for some other reason.
Bug 1770606 Comment 34 Edit History
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This should now be a lot better in latest Nightly. It's difficult for me to say how much because there are still some outstanding issues that affect screen readers (and I am a screen reader user), but these won't apply to most users, even if they have accessibility enabled for some other reason.