ECWCS Gen I was judged a disaster and replaced by Gen II that at least had vents. when that was unsatisfactory, real professional were hired and the novel concept of large-scale testing of prototypes as used to verify and improve decisions. The current issue has an insulated, water-repellent outer layer for real cold and water-repellent soft shell plus poncho for most other applications. Standing guard in heavy rain? Get out the heavy, hard-to-stuff, sorta breathable Gore-tex hard shell.
I do happen to own the Gen III system, as issued to me in 2000 while in the Marine Corps. And you are correct way better then I and II, and when worn properly and layered has always served me well. Thru many a mission and camping trip.