It can do Go.

Only ones that it can't is C/C++ (probably because that started as Apple only IDE) and .NET (that started as extension for Visual Studio).

They started Fleet that can do all of them, as a response for VS Code. But then came AI and Cursor probably took a large chunk of their users. So they redirected resources (like Zed that paused their collaborative features to focus on AI). There is currently a closed EAP for Cursor like ide based on Fleet. And their Git client as separate app.

The C++ plugin is included in Android Studio which is essentially a distribution of IntelliJ. There seems to be no technical reason for not allowing it in full IntelliJ.