(if I said it it would be completely sarcastic, but some people do idealize the far past and probably mean it honestly, presumably because they mentally imagine / assume they wouldn't be in one of the sucky classes of society)

You're contradicting yourself. You can't have "regulatory capture" and "deregulation" at the same time.

As a matter of actual fact, we do have lots of regulatory capture, which has resulted in huge swaths of regulation that favors large corporations who can afford lobbyists, and disfavors smaller business that actually are the most productive part of our economy. With what results, we see.

> They are effectively not enforced

Antitrust law enforcement has indeed been irregular since they were passed--but what enforcement has been done has done more harm than good. The classic cases of antitrust enforcement, such as Standard Oil or Alcoa Aluminum, resulted in higher prices and scarcer products for consumers--i.e., a negative impact, not a positive impact.

However, antitrust laws are a very small part of the total body of regulations that affect businesses. It's just that most of those regulations are written by executive branch bureaucrats instead of Congress. The Federal Register is much larger than the United States Code, and includes much more detailed micromanagement of all kinds of business activities. Which, again, favors the large corporations that bought those regulations in order to hamstring their competitors, smaller businesses who are more productive but less able to absorb the costs of compliance with that huge mass of regulations.