For some reason Apple puts the most basic stuff behind an accessibility option. For example, tab to next button in a system dialog is disabled by default.
And, because it’s not enabled by default any more, the implementation has regressed in various situations: I don’t use macOS normally, but I did briefly around six months ago, and I immediately found several bugs in keyboard navigation within the System Preferences app, such as where some fields weren’t accessible that way, or where Shift+Tab wasn’t the opposite of Tab (e.g. {1} ⇥ {2} ⇥ {3} ⇧⇥ {1}, rather than ending on {2}).
