There is now a “user friendly” version of Lilypond. It’s called Musescore, though a lot of the low-level stuff that was “open heart score surgery” in Lilypond has been hidden under the user-friendliness blanket 
If you go back to Daniel’s early blog posts on Dorico design, “Program C” was Lilypond. I think it has actually had quite an influence on the basic design of Dorico - for example you can organize a Lilypond project around the ideas of “players” “flows” and “layouts” if you want, though the are not called by those names, and there are other possible ways to organize a big Lilypond project, while in Dorico players, flows, and layouts are for all practical purposes “the only way”.
Lilypond does seem to have lost its way a bit since the last “released version” came out 4 or 5 years ago. They have gone down the rabbit hole of trying to tidy up the “untamed jungle” of the input syntax to earlier versions - I’m not sure how benefits from that, long-standing users know their way around the jungle already, and potential new users still don’t have a built-in GUI. But open source projects either go where the most active members feel like going or don’t go anywhere, so the “next version” will be whatever it will be, when it finally arrives.