Keep in mind many of these exercises are done under heavy EW suppression. The “own” side is usually fighting at absolute worst case scenario and the “enemy” side is using a more/entirely complete kit. That way they’re prepared for the worst.
It's not just under heavy EW suppression.
Remember the exercises where the Red army force had to face a Blue army force that had complete air superiority and also tactical nuclear weapons on demand?
But that is the whole point of an exercise. To learn from the failures.
It is definitely useful to train in a disadvantaged environment, especially if that is the more likely and realistic scenario. However it is also important to practice being able to maximize performance when operating on an equal footing with an opponent or in an advantageous setting. The requisite sophistication and nerve for decisiveness to operate well when all means are at one's disposal is a different kind of challenge that is also difficult.