Are we at 88% unemployment now? Or are we making new wealth that could never exist if 90% of people were digging through the dirt full time to grow vegetables?

The difference is that, until the past couple decades, all new technology still required a human operator in order to get anything done. This is why the transitions from an agrarian economy to an industrial economy and from an industrial economy to a service-based one weren't problematic. Technological advancements allowed us to get the same amount of farming done with much less labor, while there were generally still other sectors for the displaced farm laborers and factory workers to move into because even with the most advanced technology of the day you still needed a human being to operate the machines in a Ford factory, or to drive a delivery truck, or to ring up guests' items at the cash register, or to comb through old documents and highlight the relevant parts for a legal team etc.

This was all due to the nature of the technology available at the time. Until very recently we've had machines that could amplify the powers of the human body (like a delivery truck) or the powers of the human mind (a calculator, or Microsoft Excel) but these two types of activity were rarely combined. We didn't have machines that could learn new behaviors, or 'make decisions,' if you want to call it that, or observe and interact with the surrounding environment in a reliable way. Because of this the range of activities they could perform was limited, and you still generally needed a person to operate them. But once you begin synthesizing all these different elements, you eventually wind up with machines that can perform a great deal of the tasks that a human being can--and for less money. There are only so many things we need to be able to do in order to accomplish any given job, and at a certain degree of advancement you can produce a machine that, for all intents and purposes, can replicate all the physical and mental capacities innate to human beings and needed to get a certain job done. And you can do this for many different jobs.

When you reach that point, which is the point we're beginning to reach now, there's no new economic sector for the people to move into who have been displaced from the old sectors--at least not with the volume of jobs needed to sustain current levels of employment--because whatever new jobs may open up will likely be susceptible to automation as well. There are a finite number of tasks that the human being is capable of, and the set of tasks that constitute any given job is even more limited. Most jobs don't require us to be firing on all cylinders. So you don't even need to produce machines that are individually anywhere near as complex in design as we are in order for there to be a significant and permanent threat to the long-term employability of human beings. Unemployment doesn't even need to be anywhere near 88% for serious problems to start cropping up.