Incremental automation of any specific task isn't bad, especially if it can be introduced at a rate that's in line with the normal turnover/attrition for a job.

The doom-and-gloom scenario is when extremely adaptable and productive automation is deployed across many industries without time for the labor market to adapt, causing the world's population of 5-6 billion impoverished people to grow to 6-7 billion. Advancements in defense technology make it impossible for the masses to revolt and seize resources to revert to a pre-automation economy among themselves, so they die off.

A few hundred million shareholders and financiers enjoy their abundant luxury goods for a while, but they soon turn their robot armies against each other and also die off.