The point isn't that everyone would be happy but rather that animals (including humans in hunter-gatherer societies) have work but they do not have jobs. The difference being this: Work is when the productive activity is performed primarily for your own benefit. True, the work may be hard, it may be dreary, but to the worker goes all the reward. A job is when your productive activity almost entirely benefits somebody else. Capitalism's insatiable desire for more profit can lead to situations in which the individual is coerced into doing more labour than is strictly necessary (for yourself that is. The business you are employed for might say it is necessary that they squeeze as much value out of their employees as the law or the limits of human endurance permit.) This tends not to happen in a state of nature: No animal has to do more work than necessary to sustain itself (although maybe those infected with parasites do?).
Living on a beach is fine until some multinational company buys it up, puts a factory up on the site and kicks you off.