His point was you can’t use VSCode to ‘run’ Discourse. However, you can still use it to edit files, either for local development or even remote work.
In general you don’t ‘run’ web apps on text editors, they run as processes on the host OS.
You can set up and run Discourse entirely with just the terminal.
However, VSCode includes a terminal feature that allows you to interact with the OS however, so you can start and stop the Discourse server within VSCode.
You only really need something like VS Code when developing Themes, Theme Components, Plugins or preparing a PR to core.