If a state is important enough to indicate visually, it's probably important enough to expose to assistive technologies.

With an example such as <a href="/about" aria-current="page" class="current-page">, we now have two meanings that convey the same information: the aria attribute and the class. This can leads to bugs while refactoring.

Another example is provided with dropdowns or toggle buttons, and sorted table columns.
Mentions to :disabled or aria-disabled, :invalid or aria-invalid, aria-selected, role="tab", and the list can go on!