To put it another way, you believe that a welfare maximizing equilibrium can not only be achieved in principle, but is routinely achieved in practice with minimal friction?

This is difficult to believe. I think everyone sees signs all around them of foolish decisions by firm principals that hamper consumer and worker welfare even in the short term, to say nothing of the effect of various kinds of hysteresis on the long term development path of economies (e.g. detaching people from the labor market in a manner that undermines their health, currency of their skills, etc.)