If Vim was a GUI application (and could smoothly handle long lines), it would the perfect editor for me. Alas, the best I've seen so far is Neovim's discontinued GUI frontends.
Which discontinued Neovim GUI do you mean? As far as I know, while there are lots of discontinued ones, there are also several actives ones, see [1]. The "Activity" column in the linked table doesn't always show the correct age, e.g. vimr [2] is at least three years old.
[1] https://github.com/neovim/neovim/wiki/Related-projects#gui [2] https://github.com/qvacua/vimr