The reason the tool is not "opt-in" is because, frankly, the bias implied in "opt-in" or "opt-out" will prevent us from gathering the data required.
For a time the tool was "opt-in" (e.g., add yourself to the category) but as our needs for data grew, we outgrew the category system itself.
If you think about it, the concept of editors "owning" an article - and thus choosing whether or not it should be subject to Article Feedback - is, at its heart, antithetical to the ideals of the movement.
As far as issues not being addressed, there is an updated roadmap that includes solving for the tool appearing on disambig and redirects, as well as linking to a "what's this?" page.