I initially thought you were speaking of CPU/ram efficiency until you threw in vscode, so I think you mean developer efficiency. Vi/vim is what you're accustomed to. I've worked with nano since it came out, I think 2004-5ish. I have no idea what I used prior to that, probably vi.
But I am MUCH faster and more efficient with nano than I am vi/vim/emacs. My text editor of choice is like my IDE of choice, it shouldn't be a problem at all for anyone to just accept that I'm getting my work done in a different application.
I'm more in the Vim camp myself, but suspect that those who use nano for longer programming sessions do so using a well-crafted nanorc. Nano does support some "modern" features like syntax highlighting, it's turned just off by default. (As far as I know, you won't be getting stuff like LSP and multiple cursors though.)
It’s SO inefficient in comparison to Vim, VSCode, or tons of other alternatives.
If it’s the only thing on the box, fine, but in reality usually Vim is the only editor installed.