This would stop the currently exponential pace of growth from outpacing what society, and regulation, can adapt to. Thus avoiding the inevitable crash that will happen when we lose control of the exponentially accelerating train of technology, and it flies off the rails.
One thing you can’t accuse Doctorow of is a lack of class consciousness or failing to consider the plight of workers in a wide range of fields.
The centaur/reverse centaur metaphor instead is aimed at addressing OP’s misguided suggestion that we need to throttle tech as such, by instead inviting us to reflect which tech empowers people to do what they want and what tech enslaves people to do what someone else wants. We don’t need to “slow down” the former, and we need to smash the hell out of the latter, but most importantly we need to stop lumping them all together in the same bucket as “tech” or “AI” or whatever.