You're not wrong that greed is a persistent part of human behavior, but where we differ is in the idea that we can just "channel" it and everything will work out. That just seems like accommodation. And when you build systems around accommodating greed, you end up with exactly what we have now where corporations are shaping public priorities to serve private profits.
The idea of letting government pick winners and losers sounds strategic until you realize it's usually the biggest donors and the industries with the most lobbying power influencing those picks. That's not the government being rational and wise, that's capitalism gaming democracy.
Also, the assumption that corporations are more "controllable" than government doesn't line up with reality. Corporations don't answer to the public, they answer to shareholders. At least with government, there's a theoretical mechanism for accountability through elections, public pressure campaigns, and oversight. With corporations, once they've captured policy-making power, the public is locked out.
I don't think leftist control would make greed disappear, but I do believe in designing a system that constrains and redirects it through real accountability, and not by feeding it and hoping it behaves.