Sorry for misunderstanding. I see now that you meant autocompletion like LSP (rather than M-x minibuffer completion). Emacs could benefit from built-in LSP, I agree.

Emacs-devel are keen for it, and eglot.el is a good contender for inclusion.

Could name a single specific feature that somebody who uses emacs for years is missing? (perhaps, a link to a video if it is hard to describe concisely would be useful)

I've tried recently to steal some features from VS Code but nothing fundamental came up. I've discovered the gitlens' git-blame overlay feature but it is cosmetics (I use magit-blame). btw, the feature is available as blamer emacs package (just add the corresponding (use-package) elegant declaration to your .emacs).

I use tramp to run remote commands using Org-babel all of the time. Obviously, emacs can edit remote files just fine too. What am I missing?

> I have been using emacs for 7 years prior to switching to VS Code.

Based on what you've been claiming I doubt that.

You used emacs for 7 years without learning that it very much has auto-completion, you can see available functions with fuzzy matching, and that you can easily alias any function to any name or key-binding you want instead of memorizing it?

:-O