My strategy late game was to use 1-4 rookies as grenade/rocket troops. Especially once you got the controlable launchers. You could just have them take one step out of the vehicle and take a shot. That usually got them some experience, and deadly accuracy wasn’t as big an issue, or losing them if the worst happened. The only issue with that was mind control, so the balance of finding, discovering and using a rookie less susceptible to that was that the loss became harder. The strategy actually worked early game as well. “Ensign Smith” was sent out first, or had to throw lights if needed, etc.
The true hard part of the game was when massive UFOs/bases came into play and reaction shots, both yours and the aliens. You’re behind the curve on armor and weapons from the start, and not getting control of that early on just meant you were going to fail, it was just a matter of time.