I'd love to see a purpose-built browser that "renders" your site purely by the a11y tree, but in a layout similar to how a site might look. That'd make it super easy to see missing buttons, links, uninteractable elements, etc. I'm sure there's efforts within browser developers to do this, but it's frustrating that most of the work is being spent just telling developers their sites are inaccessible rather than giving them the tooling to help make their sites accessible.