It's certainly great advice - but for many this isn't really a reality. Even in this case, you could argue that OP could sell on other platforms (and maybe they could), but that will depend on the product and whether they need fulfillment and such.
I think more practical advice is:
a) If you rely on any given service for a substantial or majority of your income, try your damndest to build contact(s) at that platform so you have a human with a relationship to turn to when something goes sideways. At Amazon this is much easier if you're their direct customer (AWS) than a seller, though.
b) Have a contingency plan or put a focus on building savings (if it's a case like this) to fall back on while determining next steps. That could mean money for getting legal help, starting new business, etc.