That’s lovely, I’m doing the same. I’m using glfw and C++14 to build a vim-ish IDE. I never learned to love vim/nvim plugins, and make only basic use of macros and substitutions so that’s pretty much the feature-set. It’s very fun to build your own UI library.
There's plenty of things that Emacs does right, but evil-mode is far from ideal. Many plugins don't support it OOB and need special workarounds. Many others expect native Emacs keybindings and you need to manually add ones for evil-mode specifically. Nowadays I don't experience many issues with it, but this is mostly because my setup is largely static, and it took me several years of tweaking the configuration to get it in a state that's usable and intuitive for me. It's unreasonable to expect everyone else to have the same patience, so an editor with a _native_ modal UI can certainly improve the user experience.