> vim and emacs are friendly and welcoming to people who already know them; new users in 2016 have some weird expectations due to growing up using insufficiently-powerful UIs, which means that they have quite a learning curve when picking up a powerful UI.
Having first used both vi and emacs (and other text-mode - and even line-mode -- editors), though only casually then, I disagree; vi and emacs are, like almost anything, friendly and welcoming to people who have become deeply familiar with them, but they simply aren't as accessible as tools that benefit from the advances in the intervening years in making UIs easy to use for people that haven't invested huge amounts of time in familiarity.
This is really a different issue than UI power (though if vim and emacs didn't have both powerful UIs and substantially bodies of users with long investments, they wouldn't stick around in the face of their disadvantages in terms of onramp.)
Older users just didn't, when they were new, have alternatives with a simpler learning curve. So, there really was no trade off for the power vi and emacs offered (less powerful alternatives of the time were still just as inaccessible), where now there is.