There's nothing wrong with letting the capitalists run the efficiency show, as long as we are agree efficiency itself is not the goal, but a fair and fulfilling life for all people. The market outcome is not the end goal, the price system is just a way to rationalize the use of resources. Social justice and equal opportunity is the task of the state. Fuck trickle down and assorted fallacies. Progressive taxes impossible to dodge, government subsidies for education and health, massive intervention in the labor market, rentier euthanasia via macroeconomics, estate and inheritance taxes - this are the tools of the social progressive, not fudging with the incentive structure of the firm.
There is very much wrong in letting the capitalists run the economy. Until very recently, a large portion of the population (90%+) were required to actively participate in the maintenance of society (manufacture goods, distribute them, provide services). Increasingly these functions can be automated, and they will be. This situation should logically lead to a reduction in the amount of people who need to work, and a reduction in the length of service they need to provide. Capitalism however has the perverse effect of ensuring that a lack of need for workers translates into falling value of those workers. This effect causes power to concentrate at the top of society, and ultimately leads to extreme poverty at the other end. When society only requires active participation of 1% of the population, under capitalism the other 99% starve to death. That's just plain F'ed up. Capitalism worked OK (as in better than everything else), when workers were required to maintain society, this worked acceptably well. Today, it is a dismal failure of an economic policy known as "trickle down". Its time to cut capitalism loose the way the more progressive countries have done by moving to a mix of socialism and capitalism. Long term, capitalism will have to succumb entirely to something else. That something isn't going to be socialism because in many ways socialism is worse. I expect it will be some kind of socially enforced anarchy or something entirely different, that we haven't even glimpsed yet.
As a side note, the only reason companies need to grow is to satisfy the capitalists running things. In fact, companies are only needed in order to take products from the idea stage and get the products to the masses. For this, capitalism works exceptionally well, but it is not the only way to achieve this goal, and as labor is less and less needed, its evils are starting to outweigh its benefits.