I remember reading years ago about the definition of a monopoly, and that if a company amassed 50% of the market share for their industry they could start exerting monopoly power. That percentage seems low to me but if that definition holds then there are certainly a few monopolies in America. Amazon, Google, Facebook could be considered monopolies in this sense, but a very important point is there are no barriers to entry into their business, and that makes them vulnerable to competitive pressures. MySpace was also a near monopoly until it was left in the dust. Facebook is shedding a ton of users and the future is not looking too bright for them.

Cable companies had local monopolies for years until dish came around, and later streaming services. Far fewer people use cable TV anymore so those companies have evolved into internet service providers. Even their barriers to entry couldn't stop technology from out-competing them. I read the USPS is considered a monopoly (a government one, not greedy capitalists!) but that really ignores the market power of Fed EX, UPS and other parcel services. Utilities, water and power, are true regional monopolies because of barriers to entry, but they are of course very heavily regulated.

Most businesses are competitive though and while the owners of a given business would surely love to dominate their market, other free market capitalists understand that would only bring higher prices, inferior quality, lack of innovation, etc. People who believe in the free market know competition is crucial. I think I might have mention this before but it bears repeating: When i was in college my most libertarian minded professor taught a class on government regulation. This dude was as Laissez-faire as it gets. But even he acknowledged the need for government to be involved in the market for things like: preventing fraud, making companies pay for pollution and other negative side effects to society, being the arbitrator of last resort to settle business disputes, and of course to PREVENT MONOPOLIES which undermine the free market. He got it, and he taught it, that you can't believe in the free market and not believe in competition. (He even had a small section about things like corporate social responsibility and social equity believe it or not.)

BUT HERE'S THE MOST IMPORTANT POINT I'D LIKE TO MAKE: The gilded age was a very different time than today. There are many differences including education, regulation, etc. But the biggest is mobility of labor. For most of human history, until the widespread use of automobiles, 90% of the world's population never travelled more than 20 miles from where they were born. They were stuck working for the Baron or Junker who owned the local factory, and they had little recourse to finding other work. This was a situation ripe for exploitation. That situation just doesn't exist anymore. If someone really doesn't want to work for Amazon or Google or literally any company, they quit and work elsewhere because it is easy for them to hop in their car, or use public transportation, and go to a different job. That holds true for every business in every place.

So in summary, there is obviously no one company that alone makes everything you need, and that you are forced to work for. It doesn't exist, so this imaginary company you talk about doesn't OWN YOU. No one is begging to be anyone's slave.