The system is Capitalism and the markets exist within it. It makes no sense to claim that some of those markets aren't capitalist for lacking competition. In other words, while competitive markets are a characteristic of Capitalism, not every market within the system needs to have strong competition, especially because another characteristic of Capitalism is that successful competitors tend to crush smaller ones and form monopolies.
The ISP market is no anomaly but just another facet of Capitalism.
IMO fixing this should be the central push for the "save the internet" folks.