Ask HN: Why Is the US National Airspace System So Dated?

Does anyone here work with the FAA, ATC, commercial aviation, NextGen, etc.? Everything about the National Airspace System seems dated and wrong. Here's a stream of questions that immediately come to mind that all sort of convey the same thing: Why do we still talk over the radio instead of receiving instructions digitally to accept/change/deny? Why don’t controllers and pilots have the same information? Why aren’t the arrivals/departures at many major airports fully utilized? Why do controllers so frequently step aircraft down instead of letting us reach our ‘top-of-descent’ and utilize more efficient vertical navigation capabilities? Why are new aircraft, with processors from the 80s, considered "advanced"? Why do I get slowed down, then sped up, then slowed down? Why don’t controllers just control the aircraft themselves from the ground since they’re the ones who know what’s happening? Why are so few airlines approved for LPV (and why do we still use ILS)? Why is it true that an airline pilot today could operate in 1970 without missing a beat (the competent ones, at least)? Why does my job still exist? So much more is possible, but nothing seems to change. Source: Current airline captain.