Where does the person with severe anxiety go from here?
Being aware is the cornerstone of any successful person. These aren't just platitudes they are the very foundation on which emotionally healthy secure people stand.
What solutions does one get from this?
I agree 'To reliably reduce one's level of anxiety is extremely simple, just stop doing anything,' this is a false statement. It takes years to reduce one's level of anxiety. of course a dead person has no anxiety and simply reducing ones anxiety shouldn't be the overiding goal of therapy. Taking meaningful action should be. But if we look at the context of the mind, and day to day social interactions, not doing anything, as in not reacting to the thoughts but just observing them is the way to go. It allows you to focus on your body and from there you can foster your intention whilst remaing in the present moment.
What does a person with this severe condition do then?
Maybe take a meditation bootcamp, take a yoga course, do mindfullness exercises there are many ways to learn to observe ones thoughts and become aware of the present moment.
Just stop doing anything? Just be mindful? just stay in a state of relaxed awareness?
Dont dismiss these things they are vital in learning to be more effective in the world for the socially anxious and really for anyone.
You sound like you have a strong opinion on the cause of social anxiety although you say it does no good to dwell on the topic i get the feeling you still carry insecurites around this, as do I there is nothing wrong woth having insecurities everyone has them. but ask yourself the question 'is it effective going forward for me to have these beliefs' as I suspect probably not in which case explore the beliefs. Ironically the best way to explore them is to observe them using mindfullness which you've dismissed as 'no real cure' when in fact its the cure you need.