I agree that the learning curve is steep. That said, everything described in the above paragraph is covered in vimtutor, which takes about half an hour to get through and is well worth it. Vim cheatsheets are also a great resource when you're new to it. I do think the default settings could be better though (e.g. "set nocompatible" should be enabled by default, otherwise you're missing out on 22 years of progress).
Take a look at vim-qt - I've found it works much better than GVim.
That said, I suspect the main reason for writing Neovim in C is the desire to not fragment the codebase too much, so that there's the possibility of merging the changes back in.