Wouldn't it be the other way around? There would be more things you'd have to simulate for the 2nd gen jets, and the 3rd gen jets would have it left out. For example an F-15 when firing a missile, the computer takes care of everything, you just lock on and fire, whereas firing a missile with a Mig-21 is much more complicated and requires the pilot to do a lot more than just lock on and fire.
Thanks to whoever suggested Wings Over Vietnam, I hadn't heard about it, checking it out now.