The first Gen air to air missiles were unreliable resulting in the Top Gun program. Today the air to air missiles are so good, the enemy will still be looking when they lose a wing.

This specific AR program was doomed to fail. Just look at Army procurement the last few decades, and those aren't bleeding edge technologies. Processors and responds times simply aren't fast enough yet, the battery life isn't there yet in a convenient package. However the fact is every game knows how powerful effective hud elements can be to gaining an information advantage. Whether it's integrated target tracking with squad mates and weapon systems, to just seeing things easier. Near peer states are going to have night vision and infrared vision. Soldiers won't be able to use infrared lasers without giving away positioning. A reticle in your hud for your rifle can give significant advantage.