Thanks for the comment. Respectfully I do not feel enough considetion is being put into the default state in many situations.

I have worked on 4 separare systems that have successfully used 3:1 ratio on interactive elements and still had enough room to design meaningful states. It is entirely possible to do, especially when not relying on colour alone for these distinctions. In fact I think it's a good challenge to set yourself.

The Facebook input example is 1.33:1 (admittedly over 4:1 when autofocussed - but this autofocus is removed by the cookie banner before anyone can interact with it). I don't think this is a ratio that can be justified to have greater separation of states.

For what it's worth I also design for a minimum of 3:1 on :focus states too, again...entirely possible when you don't use colour alone.