I don't get it why the hell is TypeScript still not nativly supported in modern browsers?
Because "it doesn't exist". It's just a layer on top of js, it doesn't have its own runtime, and btw what would supporting ts a the browser level mean? If you want to support a static typed language then you could just compile it down to wasm, if you just want to support types and ignore them at runtime there's an overhead price to pay, or should do runtime type checking? And with which tsconfig? Strict or not?
Python supports types and is interpreted, right?