Isn't there already laws against established companies using their market position to price under cost to cut out competition?
There are laws against 'dumping', which is selling goods at a loss to drive out competitors, but those are fairly narrow in scope. It would be hard to enforce a more general restriction on not being profitable.
I really have no idea. Since the market values uber or a buy now pay later widget (or at least used to) at 50+ billion I'm not sure I understand much how things work. Maybe we need a reluctant philosopher king like in Plato's Republic.