Saying it hasn’t been built in 30 years is a bit misleading. Although the base Il-76 airframes may be that old, the latest substantial avionics upgrade (designated A-50U) is less than 15 years old or so (first delivery in 2011), which isn’t too bad for military and aircraft systems. A lot of the E-3 equipment is older. That is not to say it is more capable than the E-3, it probably isn’t, but I’d say a fully functioning A-50U should not be underestimated. It’s even got toilets! Then again, it is also not clear to me that any “U” models are currently airworthy.