One thing rarely mentioned is what happens when all the white collar people lose their job and can no longer pay for expensive blue collar work?
Those who can, will, those who can't won't - and in response to the question posed, those who can no longer afford will either have to learn how or put up with decay creep.
Obviously there are practical limitations to how fast things can rearrange but there's no reason in principle you couldn't have an economy where everyone retrained into blue collar work, and all white collar job needs were handled by the magic internet box.