I like the concept and the aesthetic of the game. I would suggest just straight up copying a lot of the controls from total war, no one is going to complain about that. Things like rotating the camera with q/e, unit control groups and unit control cards.
Would be nice to gradually introduce new unit types, you have a bit too much to manage at first here. I'll talk about more general stuff though: Collision seems like an issue. Units bunch up together a lot. I had 4 tank destroyers that I ordered to attack 1 enemy tank destroyer, they all stacked together, got hit first and they all got stunned and soloed by the 1 enemy tank destroyer and that felt really awkward. They also went up really close, it's kind of difficult to tell how far units can fire, it would be nice to have some sort of range indicator or some indicator that they don't have line of sight on the target. I also had no idea that the green units are allies at first, it makes sense once you see enemy units but if you haven't seen any yet its kind of confusing.
I know good unit collision is a difficult issue to handle in 3d strategy games but I think it really improves the feel a lot so it's something I would focus on. It's more obvious for melee combat where you want to take up space and block others from getting there but it's still relevant for ranged combat because it's a natural way to prevent bigger armies from steamrolling everything by making it more difficult to have them all in a position to fire.