That sounds good on a surface level analysis but closer inspection of how political correctness has changed over the last century suggests it's actually not at all as simple as you make it out to be. We're actually crap at pulling it off.

If it requires communication then the formulation is actually closer to "treat others how they state they'd like to be treated". We're getting further and further away from the original formulation.

Think of it another way... If you were a 19th century man, it's not likely you would have a cordial chat with a woman or a gay man, deploy empathy and come to 21st conclusions on how you should treat them.

The change is hard fought and hard won. How we state we want to be treated is a matter of both public and private discourse and it's a long process for enough communication to happen for the baseline of what social norms should be to shift in a noticeable way.