What problem does this address?

The data-wp-ignore directive is designed to prevent hydrating a specific part of an interactive region. However, the current implementation breaks context inheritance and could cause issues with client-side navigation. Supporting these cases would be complex.

Moreover, it doesn't cover a real use case at this moment, so the best option would be to just remove this directive.

What is your proposed solution?

We can display a warning message when data-wp-ignore is used and remove it in a subsequent WordPress release. Alternatively, it can even be removed directly, as it is not documented and it's improbable that developers are using it.