Although vim has a lot of shortcuts and commands, you don't need to use all of them. After learning a few essentials, using vim is way faster than any other IDEs or even text editors. Also, it's highly customizable with a .vimrc file.
Vim is very configurable so it can be made to perform as an IDE. However out-of-the-box, it doesn't have many things associated with IDE's (concept of a project with project specific options, integrated debugger, context aware auto-complete).
Qt Creator has a code model which basically has the same information as the compiler. So it can do really nice syntax highlighting (e.g. of virtual methods or local variables) as well as provide great code completion.
The UI is fairly boring and has limited customization options. There is a dark theme available, however it only applies to the editor. The surrounding windows and borders remain light. You can see a collection of screenshots here.
Sublime Text, while being lighter-weight than an IDE, still supports many IDE features. Text from the current file is used to provide autocomplete. Project Support (folder browsing, scoped history, build-system declarations). Refactoring support is emulated through multi-select, project-wide fi...
Vim plugins have always been useful, but tied to specific languages. Neovim's architecture provides better separation between plugins and the core product, so that plugins are completely flexible and can be written in any language.