I think your proposal of automated buying and selling should certainly be explored if it hasn't already been considered. However, I disagree with your position that the current gameplay doesn't represent what a "good" CEO would be doing under the specific circumstances presented by the game.
In the backstory of the game found under the "Game" tab at the top of the page, we learn that Offworld Trading Company takes place in a world where Earth suffered from an event known as "The Great Collapse", which is apparently a global market meltdown at least partially caused by automatic transactions and rogue AI. The markets in the game are designed specifically to prevent this kind of disaster from ever happening again, and one of the protections seems to make it so only people with a certain degree of authority are permitted to make large scale purchasing and selling decisions, for which they are personally held accountable. The new economy ensures that rather than hiding behind a shield of underlings or computer programs, CEOs are themselves responsible for the success and failure of the company.
Plus, delegation is present in the campaign's metagame. The CEO only sticks around for the first week or so of settlement and then moves on to the next struggling colony. It seems entirely reasonable that the CEO would want to get extremely hands on in that crucial early period, and then leaves the decisions of daily management in the hands of an underling only when things have calmed down and the opposition is beaten.
Add to this the indications that these are small companies, with employees in the dozens (or maybe in the low hundreds at higher levels), trying to make the best of a rather desperate situation. The vast majority of workers in a scavenger colony are probably just trying to keep the jury rigged equipment from tearing itself apart, most of a science team are probably actually engaged in research rather than production or management, a robotic colony is heavily regulated AI that is not allowed to overly upgrade or reproduce itself, and if anyone in an expansive colony isn't doing three jobs then they aren't working hard enough. The companies perform like startups, like at Mohawk Games where Soren has to do a lot of the gameplay design, testing and marketing himself despite being the founder of the company.
Of course, in it's ultimately a gameplay decision, not a lore one, but the fact that they have clearly built explanations for why things don't work the way you propose way into the backstory on a fundamental level is a pretty strong indication that they have already given some thought to the idea. My guess is that manipulating auto-sell and auto-buy prices to be optimal in an ever changing market would also require a great deal of micromanagement and allowing players to directly engage with the market was considered to be more intuitive or satisfying. That said, while I like how the game currently plays, micromanagement and all, it's certainly in the process of evolving and I'd be certainly be willing to give an alternative a try if the designers found that it worked well.
