Infantry worthless? This certainly does not match my experience. In fact I found the basic rifleman to be the most powerful unit. Once APCs come available for GDI APC with Rifleman driving into the enemy's base to take out the MainBuilding was the only tactic I used (and needed).
A group of Rifleman makes short work of any building with a frightingly fast pace.
Ot topic: I've finally settled on Ghost of a Tale and I'm really enjoying it. It just took a couple of hourse to "build up steam".