Of course there are edge cases, I work with accessibility too, for an app in the public sector where WCAG rules are no joke, so I know this as well but even so, we don't build custom accessibility UI for our users. We (try to) build the UI with accessibility in mind so it's scalable, can be used and navigate properly by voice over and keyboard.
On mobile it's not perfect either but in general you do have features to change stuff like. focus, grouping of elements, how the keyboard navigate the view stack, how to access a button through custom actions and like you mention, change the tab index programmatically.
Even so, not everything can be fixed or handled through standard accessibility means and as such hacks will inevitably make it into the products.
I get what you're saying but I still think that making things accessible and designing with common accessibility in mind should be default and as such it has to be thought about when designing and developing from the get go. Having to create custom interfaces to fulfill a specific need might be a good fit for some things but not when developing apps and websites unless you're targeting that user-group specifically.
On mobile it's not perfect either but in general you do have features to change stuff like. focus, grouping of elements, how the keyboard navigate the view stack, how to access a button through custom actions and like you mention, change the tab index programmatically.
Even so, not everything can be fixed or handled through standard accessibility means and as such hacks will inevitably make it into the products.
I get what you're saying but I still think that making things accessible and designing with common accessibility in mind should be default and as such it has to be thought about when designing and developing from the get go. Having to create custom interfaces to fulfill a specific need might be a good fit for some things but not when developing apps and websites unless you're targeting that user-group specifically.