The actual problem with technocracy (if done right) is that the work of experts grows increasingly incomprehensible to average men. Even if things work out perfectly, experts can't properly take risks or make a leap of faith in other people's name. (Not to argue our current democratic model is any good at it)
That's a recipe for disaster. The technocrats define who can be a technocrat, and can design the process to benefit them. The incentives are towards elitist, racist, cronyist policies that would select for sociopathic tendencies.
What's the difference between a technocrat and a bishop in this case?