You need a network of people you can trust, or build some fake lifes, or do a lot of things in parallel of the system. Most of the time all of them together. It's work, but it's possible.
The problem is: it's more work for ordinary people. The systems in place are making it difficult for citizen to exist outside of the system, change it, or express differences. But it doesn't make it as difficult for criminals to be criminals, because those accept destructive consequences of their acts.
How do you plan on doing that if most stores and banks stop accepting cash, and to get a debit or credit card you need to show government ID, which is electronically verified (it has an RSA keypair, signed by the government, stored on its chip).
Most stores don't stop accepting cash right now, and I doubt they will in the future. I know more shops refusing credit cards than ones refusing cash in France.
You can also live without a bank. Several people I know do so. Again it's work, but it's possible.
A lot of the time, people saying it's impossible really are asking "how can I keep my confortable life 'as-is' while going off the grid". THAT is impossible. You can't live your current life, because it depends heavily on the system.
The problem is: it's more work for ordinary people. The systems in place are making it difficult for citizen to exist outside of the system, change it, or express differences. But it doesn't make it as difficult for criminals to be criminals, because those accept destructive consequences of their acts.