What’s the appeal of an editor like Emacs in 2026? Why’d anyone still use when most jobs nowadays require you to work inside a container (and therefore use VSCode container extension)?

Can't you ssh into them? If so, in emacs you can just open /ssh:host:path/to/file and remotely edit that file.

Even if you didn't have emacs, I don't think you are forced to use VSCode. You could just use sshfs and use any local editor, but I guess other editors also have remote editing plugins

I was using TRAMP to do that in Emacs 20 years ago. These days I use emacs-server in the container and waypipe my frames.