Assuming (1) the replacement is a better solution, and (2) it is feasible to retrofit every aircraft in the world and switch everyone over to it.

Just in relation to (2), I can't really think of anything worse than having two communication systems on operation at the one airport - everyone must be using the same system.

Nor will it be a good argument in case of a fatal crash to say "well, it did contribute to this terrible accident, but in the long run it'll be better for everybody!".

Nobody in aviation is conservative about automation due to a lack of a desire for safety; quite the opposite. But it's just a fact that e.g. an automation system that can prevent a type of human error entirely in 99% of all cases can lead to more accidents in total, if it means that humans aren't regularly exposed to these 99% of cases which in the end train them for the 1% that the computers can't handle.

And this is, as are so many things in aviation safety, learned through blood.

You seem to have a pretty strong but not necessarily very substantiated opinion about the topic. I really suggest you read a bit about it, if you're so inclined. E.g. Admiral Cloudberg has been mentioned in this thread, it's a very good resource of accident recaps and the impulses they give for regulations and developments.

In contrary to what you're implying, "we've always done it like this" is not a principle of aviation safety.

Indeed you'd be hard-pressed to find any other globally coordinated system that is so dedicated to and successful at the gargantuan task of continually improving itself, a trillion dollar industry, and regulatory bodies all over the world. A five decades long track record of drastically reducing fatalities in the face of rising passenger miles speaks for itself.

To put it a bit bluntly, I'm pretty sure they don't need to be told that it would be "just as simple as (...), because that works for an elevator".