The thing about technocracy is that there need to be human concerns and philosophies driving whatever scientifically-driven policy-making it's being done.
Do it wrong and that's how we end up with eugenics. It's incredibly easy to justify horrible stuff using metrics, the essential questions that cannot be overlooked is what metrics ought to be valued and why, and science is not the right method to make the ultimate judgement of what the values of a society ought to be.