Given that I love Emacs, I hate to disagree with you, but I must:
This is like a car model that came into existence 40 years ago, but is still making cars today.
Ford is over a 100 years old. Yet I have no problem getting into a rented Ford and driving without consulting the manual.
As someone that used to drive a lot of rentals, I think you overstate how seamless it is to get going in a car. More, I think this glosses over how difficult cars used to be, to operate. With how unreliable early spark plugs and carburetors were, it is hard to state how far things really have come.
And my point is I agree that vanilla Emacs can feel spartan. Thing is, my customizations have aged really well. My config for Emacs hasn't changed too much in over a decade. That kind of stability is hard to put value on. Especially when our industry seems to price itself on instability.
Even better, compare it to driving a boat, when you've been used to cars. (Or, for that matter, realize that it is a stick shift car when you've been used to automatic. And slowly realize everyone has a slightly different way to get their system running as an automatic.)