This is true, but it demonstrates that VSCode extension model supports this, and nothing stops extension developers from attaining the same level in any other language. Hence my point about IDE/editor distinction.

Sure, why would it not be possible. Intellij and Eclipse also implement all their language support in plugins so why wouldn't VSCode.

But the thing is this is all hypothetical - it is possible if somebody invests those thousands of hours into it. But so far it did not happen for most languages and Intellij IDEs are still vastly superior to VSCode for e.g. Java, Python or C++ development.

Fair point, though I'm skeptical whether extension can achieve the same level (and performance) without vscode optimized for that.

The TypeScript support is implemented as an extension.