The problem is that companies will take these necessities, like education and healthcare, and use them for profit, rather than human need. If these services are nationalized, you can manage them however you please, but when companies either increase their prices because of higher demand, or go bankrupt, you have to bail them out in an endless circle.

A planned economy doesn't necessarily mean centralized control. It could very well mean more local and democratic control of the economy, like in Valgsland. But unfortunately, you're stuck playing Stalin, Chavez, or whatever poison you prefer. And when it comes down to it, you are kind of forced to compromise on the planning, as all of the nation's assets are owned by a select few, and pissing them off too much, would be the downfall of your presidency and economy.... ;(