I wouldn't qualify them as that, and neither did Tesla. Not everyone is the right fit for the job they are currently working. People can struggle with a job for any number of reasons.

Companies will very rarely propose a pay-cut, but more likely they would just rather find someone else. Because they have specific jobs that needs doing and can't afford to have something done poorly.

Even if hiring was perfect there would still be rational reasons to fire sometimes. And hiring is far from perfect.