One has a choice between learning enough about Vim to replicate arbitrary workflows/functionality in it, or using other softwares that do those things out of the box and clicking the "Vim mode" check box in the settings.
Both are perfectly valid, but they are going to appeal to different kinds of people, with different priorities.
I think there is a difference between features of the editor and editing method. Following your logic - if there is already Notepad, why create TextPad, Atom, Word, VSCode etc...
I'm a heavy user of JetBrains IDEs for most of my development work and use it with the excellent IdeaVIM plugin because modal editing is my preferred input method.
I have all the goodies and features of the full IDE with the keybindings and modal editing muscle memory I've built up over the last 15 years.
Technically I can get Vim to do most of what JetBrains does but that's a very very big hill to climb.
vim is not an IDE. You can make it IDE-like with plugins and integrating third-party tools (e.g. for completion, refactoring, debugging), but it is still not one. You may not care, but come on, it's not that hard to understand.