"New Economics"???

I have heard many people say things like:

"Yeah, capitalism worked for early America, but would never work nowadays." or "The times are different. Having a free market now would be like having democracy in Ancient Egypt... it just wouldn't work." or "Are you denying that we have entered a new economic paradigm?"

If people are going to try to use a scientific/historical approach to economics, it makes little sense to say that the rules changed all of the sudden. For people who think we have a new economic paradigm, they have thrown their ability to use history as evidence out the window.

Just to be clear, I do not remember hearing those arguments used on this forum... but in my every day discussions, those myths sometimes arise.