We never had a capitalistic economy. Though taxes and regulations at the federal level were minimal early on, some states did tax and regulate, and federal the government imposed substantial tariffs on foreign goods protecting US business interests.
However, we're not moving towards Marxism. We're moving towards fascism. A Marxist economy would mean the government was actually seizing private industries and directly operating them. For example, true "socialized medicine" would mean that all health care facilities (hospitals, clinics, doctors' offices, etc.) were owned by the government and that all doctors and their staffs were government employees. There are no private winners in a Marxist economy.
Instead we're seeing the largest businesses in each industry (basically cartels) jumping into the sack with government. They're accepting regulations and having to put up with unions in exchange for suppressed competition, bailouts, liability protections, tax loopholes, and government contracts. That's more indicative of a fascist economy, and of course, if you're one of the few lucky enough to be in the cartel, you're a huge winner, while everybody else loses.
Our current leaders are more like Hitler (without the concentration and death camps) and Mussolini than Lenin or Mao.