Capitalism requires fair competitive markets
It might seem that way if you don't know what capitalism is.
all the competing companies have been allowed to amalgamate into a few or a couple.
You are so close.
All you have to understand is that capitalism means one thing, which is that capital controls the means of production.
Massive consolidation is an obvious consequence of capitalism, and abuse of consumers is an obvious consequence of that consolidation. That's why antitrust law exists, but it is not capitalistic. Antitrust law is the opposite of capitalism. And that's why it's not being enforced meaningfully any more — because capital controls that, too.
It seems to work like this: Anarchy leads to feudalism leads to any of a number of inefficient systems lead to capitalism leads to failure as the capital eventually takes control and breaks everything. The only question is where you go from there. Will it collapse all the way back to feudalism, or even anarchy? The former is much more likely than the latter. A number of authors predicted techno-feudalism, including Neal Stephenson and Margaret Atwood.